I have noticed that buying some weapons like P90, shotguns or auto snipers will get you called out for that. However, none of the players telling me that using those guns is nooby have provided any real reasoning, nor have I found any reasoning when asking the almighty Google.
So, I am asking:
I can't speak too much past what others have said on what specifically are seen as "noob guns" in CS:GO, but one thing I haven't seen mentioned yet that I think factors into what eventually get called as such are their skill floors and ceilings. In other words, how effective is a weapon when you first pick it up versus after you've used it for tens, hundreds, or even thousands of hours?
A classic example is the "Noob Tube", i.e. the under-barrel grenade launcher attachment, of old COD games (I've only played MW2 and Black Ops, it may or may not still be a thing). The skill floor was practically zero because you could just aim in the general vicinity of someone, out to decent ranges, and often get a one-shot kill. On the other hand, if I remember correctly, it was slow to reload and had a small ammo capacity, so past that first potential kill, you weren't likely to get a whole lot more out of it. Plus, while it was some degree of effective out to mid ranges, it was literally a random lob-shot anywhere past that. Thus, it was satisfying for beginners because at least they had a good chance of getting on the board with each spawn, but it was also unlikely to allow you to carry a game. Almost any other gun would provide you with higher potential and flexibility once you got good at the fundamentals of the game.
On the other hand, whatever happens to be the most powerful assault rifle in a given game tends to have high skill ceiling. The AK in CS:GO is a guaranteed one-shot headshot, which means a higher-skilled player using it gets rewarded with shorter kills, leading to more health left over to finish off the next guy. The AWP in particular is a great example, because someone with good reflexes and general ability to click on people can get incredible results from it. But, in order to be good with these weapons, you usually have no choice but to practice with them and understand the subtleties of that specific gun's mechanics. Not always, but much of the time, playing with other guns just won't translate much towards being effective with the theoretically strongest ones.
This of course goes past just guns in FPS's. It extends into nearly every competitive game, where certain weapons, tools, or characters provide more immediate results at the cost of eventually not being able to improve because you've more or less "mastered" them. Another example I'm familiar with is Overwatch, where heroes like Genji and Ana are very mechanical and difficult to learn but have almost limitless potential, while others such as Mercy and D.Va (the latter of which I mained for quite some time) are easier to grasp but can rarely pull off the really insane stuff that the first two are capable of, no matter how good you get with them.
So while certain weapons that get labeled as "noob" guns can be very effective at what they do in certain situations (and often should be picked up at those times), they can also become a crutch if you use them at the expense of getting practice in with the guns that are harder to use but also have a higher potential. Personally, I've never really been great enough at a given game to make skill ceilings matter, but I'm sure everyone here knows that many, many people online think they're the next MLG pro and think that everyone must play as such.
Noob guns are usually called that way, because they're hardly used in e-sports matches and getting killed by it makes people look bad (which actually isn't true at all, they're just mad). The Counter-Strike community can be very toxic when it comes to weapon choice (equal to the MP7 in previous CoD titles), because they're pretty easy to use in public games. I've seen people calling out everyone who did't use M4 or AK, because they're the weapons everyone "has to use".
The weapons you mentioned are really easy to use, but they don't work everywhere:
Auto Snipers require a decent spot, some coffee and just enough time to wait for victims.. someone will eventually run into you and is most likely dead soon. So a camper has the biggest profit = "noob", because they just sit there camping all the time. You can easily defend a bomb site with it, even against a rush. Doing that with a normal sniper is way harder.
P90 is a typical run and gun weapon and pretty cheap to buy as well. Personally I like it a lot on fast paced maps or to counter eco rounds. Throw a flash into a tunnel or room, jump in and spray & pray - ace. It's not a noob gun at all, but people think it is, because you can do a lot of damage with less aim than with rifles, but those just work differently.
The shotguns are indeed unwanted in a lot of games, because you need no aim at all to kill people. What they forget is how to counter them. Just don't go near them, because they're only effective in close proximity. Defending a bomb site with it can be fun, but the attackers will hate you for it, so it's a "noob gun" because you chose the right weapon for that round.
Also there is no list of what's a noob gun and what's not, because this is highly subjective. It's more a selection of what weapons work in what situation and that always depends on map, enemy and economy. Just don't buy Heavy MGs too much. The impact on your eco is too big to be useful.
Although the submitted answer by dly is quite on point...
The problem with the "noob weapons" comes from older CS games where the (Terrorists in particular) auto-sniper was very frowned upon as it was very easy to hit shots with, had incredible damage output and was generally less-skill per kill. Also the no-scope accuracy while jumping ruining crouching etc was I'd say about 100%.
This has then evolved in (as stated in the other answer) considering pretty much any weapon other than AK/MK/AWP as noob weapon.
People don't like investing into a full buy, MK, nades, 100armor, maybe even a pistol and a zeus just to die by a random spray and pray from the enemy on the other side of the map. When this would happen people would very frequently get very mad and try to vent anyway possible, main one calling out the enemy for their low skill and noob weapon.
Those same people don't realise that the spray-and-pray noob weapons are less accurate, have less damage and would loose out against a good AK/MK player 99.9% of the time.
Those same people also don't realise that maybe while they were practising their one taps against players with AKs and M4s, I was practising my run and gun control against the same AKs and M4s. Maybe, just maybe I deserved to kill them as I've put the time to not only control the spray pattern, but to also control it while both you and me are moving. Maybe I deserved to kill you with a much less superior weapon because you failed your initial engagement with me and didn't stop me with a well placed headshot.
But people don't go into the why, that deep. They are just salty that they died from seemingly less skilled player.
Play with any weapon you like and don't concern yourself with the saltiness of other players. When they die like that, they get mad. When they are mad, they make even more mistakes, and more mistakes means more wins for you.
Adding to the other answers, I want to provide a more general view of the problem, which I find is very well described by David Sirlin in his book "Playing to Win". I'll try to find a balance between a link-only answer and just copy-pasting his stuff.
So let's say a "noob gun" is a weapon mainly used by "noobs" or "unskilled players". There is nothing wrong with that, everybody has to start somewhere. But I often hear that complaint about "noob guns" from the team that is losing or the player I just killed with it. There are multiple issues with that:
Most other answers here already explained that, most of the time, there is no "noob gun" that is superior in all situations. They may be awesome in some situations, but useless in others. A well-balanced game should offer a rock-paper-scissors kind of mechanic, where each tactic or move has a counter. That counter can be countered by another counter, and so on ...
And often the best way of discovering a counter is by using the "cheap move" yourself and getting beaten by someone else, learning when that move is useful and when not.
Sirlin uses the term "scrub" as someone who calls certain tactics, moves, weapons "cheap", so in this case the scrub would be the one claiming that some CS:GO weapons are "noob guns". (Sirlin made his gaming career in Street Fighter, but this is just as an example and you can transfer almost everything he says to CS:GO or other games.)
I'll just quote a small portion of the chapter "Introducing...the Scrub" and highlight the parts that are probably answering your question:
In Street Fighter, the scrub labels a wide variety of tactics and situations “cheap.” This “cheapness” is truly the mantra of the scrub. Performing a throw on someone is often called cheap. A throw is a special kind of move that grabs an opponent and damages him, even when the opponent is defending against all other kinds of attacks. The entire purpose of the throw is to be able to damage an opponent who sits and blocks and doesn’t attack. As far as the game is concerned, throwing is an integral part of the design—it’s meant to be there—yet the scrub has constructed his own set of principles in his mind that state he should be totally impervious to all attacks while blocking. The scrub thinks of blocking as a kind of magic shield that will protect him indefinitely. Why? Exploring the reasoning is futile since the notion is ridiculous from the start.
You will not see a classic scrub throw his opponent five times in a row. But why not? What if doing so is strategically the sequence of moves that optimizes his chances of winning? Here we’ve encountered our first clash: the scrub is only willing to play to win within his own made-up mental set of rules. These rules can be staggeringly arbitrary. If you beat a scrub by throwing projectile attacks at him, keeping your distance and preventing him from getting near you—that’s cheap. If you throw him repeatedly, that’s cheap, too. We’ve covered that one. If you block for fifty seconds doing no moves, that’s cheap. Nearly anything you do that ends up making you win is a prime candidate for being called cheap. [...]
Disclaimer because of some confusion: This answer is written from a competitive view on the game. Playing to get good, rank up and score. If that is not the intention of the OP, then this might not be of much help.
Although Иво Недев said
Play with any weapon you like and don't concern yourself with the saltiness of other players. When they die like that, they get mad. When they are mad, they make even more mistakes, and more mistakes means more wins for you.
I definitely cannot underline this enough! Of course it all depends on what scope you play CS:GO. I, for example, with almost 1k hours in, am playing competitive, to win, to rank up, to be good, and hate it when my teammates goof around or play with weapons that are just not worth it. And some of them you mentioned are these guns (Auto Sniper, Shotgun, P90 to a lesser extent). There are situations when a weapon is good, but not EVERY weapon! And there are some guns that are simply objectively better than other. So why play with inferior guns? To me, that implies that you are not invested in the round, and a possible threat to my win! And when people loose because other people don't play seriously, that puts some people off, including me. Of course, I don't rage around and call names, but to me this has something to do with respect. Respect for your teammates by giving your all and playing with appropriate weapons for the right situation.
And for the question which weapons are not good and why. As already stated by other answers, most of these inferior weapons might seem powerful and op at first glance but are really really easy to counter. Let's take the P90 vs someone with an AK for example. The P90 lets you rush in and spray someone away easily, but if you have bad luck, or a good opponent, he taps you 1 shot in the head (AK is 1hit headshot kill) and you are dead. And in longer range the P90 has not even a chance against a good AK user. Shotgun the same game. And auto sniper are just not worth it. Let's compare AWP vs SCAR. SCAR lets you shoot much faster, and when you are a bad sniper this might help, because you correct your miss faster BUT you will need 2 hits mostly, but when you are off against a good AWP'er, he will have the upper hand because he just need 1 hit (except for legs) and you are dead.
So, as you can see, there is a REASON why some weapons are inferior to others, and there is a reason why you should not play with them. That's why it is really important that you practice and play with the guns that have the most potential as AK/M4/AWP. It is just as it is. And it shows respect for your teammates by giving your all to win the game! :)
The reason why they are considered noob guns is because newer players use them, as the more commonly used weapons such as AK-47 and M4a4 require more skill to use (meaning spray pattern learning, fire rates, aiming accuratly.)
For example the P90 can be used semi-accuratly whilst running. (But if you were to do this against experienced players you wouldnt stand a chance.)
To identify a noob gun, often the easiest way is anything other than M4, AK, AWP or Anything vs Eco round. Noob guns are usually low recoil low damage with the exception of things like the auto sniper and scoped rifles.
The reason why the auto sniper is considered it is because its not very mobile and costs way to much for its dmg output (2-3 bodyshots to kill, AK requires 4) $5200 vs $2700 (the prices are guessed as i cant remember from memory.)
The scoped weapons are a similar arguement, more expensive same amount of shots to kill. The only added bonus is you get a zoom in sight.
Hope this clears things up. Also if people call you out on it, its either because your at a rank where these guns are not used anymore. Or they think they are some sort of professional silver/nova player.
Something that I feel is not covered as much as it should be is that when a player is accused of using a "noob gun" they may often actually be using a "noob strat" and then the weapon is unfairly blamed. While much of this discussion can be transferred to "noob strats" as well, there's one specific examples that I want to mention:
I (MG2) once played a team that on CT Mirage bought shotguns every round and hid randomly in one of the two bombsites (the entire team in the same site). Now, at our level their strat was fairly effective when we attacked the stacked bombsite. They had clearly practiced doing this and using shotguns. In addition to this, Mirage was a map that lends itself particularly well to hiding in bombsites. Now, was there a counter to this? Yes, of course. Learning all the hiding spots, learning how to peek them one at a time using the entire team, and learning the relevant smokes and grenades would all have helped much. But in this game, at this time, my team did not know this. As a result, the outcome of each round was largely random, based on whether we hit the right or wrong bombsite. Needless to say they never succeeded on a single retake. This is the key to why something like this is considered a "noob strat"- The outcome of each round is largely randomized. Neither us or the other team can do much through out the course of the game to help us or themselves. Even more importantly, the other team had gotten to this rank with significantly less work and less effort than we had. Essentially, they were duplicating our success with a fraction of the effort, and offering us no option to fix this within the game. Now, was this a sustainable way to rank up for the other team? Of course not, and I imagine that they are still stuck at MG2 while most of my team has now ranked up past that. But that's not the point. Right then and there, we had no other options, and they almost won against us by pure chance.
While this is touched on in the accepted answer, the aspect of randomness in something like this is not addressed. Noob strats and guns are nooby because they succeed from RNG, and not real skill. This makes other players (somewhat understandably) mad, and certainly doesn't help prevent a toxic community.
Edit: I see that this answer warrants some clarification. I didn't want to repeat what was said in the accepted answer, but I'm going to go over some of the same things, and append to them. Specifically, the idea of skill ceilings. Every weapon and strat in the game has a limit to how successful a team or player can be with it. For some strats, see above, the skill ceiling is fairly low. For other strats it is rather high. This is covered thoroughly in the first answer, so I won't go too far into depth here. The point I'm trying to make though is concerning what happens above the skill ceiling. Specifically, a lot of what happens above that is controlled by RNG. Take for example, a spin bot hacker. Effectively, all this hacker has done is taken the RNG and forced it into their favor. A spin botter can easily beat all professional players, even with a poor weapon. This is the key point. Every bad weapon can become significantly better when the RNG works out in favor of that player. Now, at professional levels this doesn't work all too well, because the chance that a P90 spray and pray will kill an AK player faster than the AK player will kill the P90 sprayer is nearly zero. On the other hand, at lower levels, this becomes quite possible. Now, let's look at this from the low level AK player's perspective. Someone who has put almost no work into their game can win against someone who is practicing, trying to get better, and has a chance of becoming a good player at some point in the future. At this point, it's no surprise that the AK player might get mad and start yelling "N00B" in chat.
Two more things:
You asked what guns are considered "nooby guns". The short answer is: none of them. The long answer is that it depends. All guns in CSGO have a legitimate, if very specific, use case. However, in 9/10 cases most of the guns that are called "nooby guns" are not used in this way. A great example of this is the shotguns. Professional players have found success with them in places such as drop room on Cobblestone or ladder room on Train. However, this does not mean that you should buy shotguns and try playing those positions. In CSGO, weapon buys is a strategy that needs to be coordinated by the whole team. If you go ladder room, you need to make sure that your team can and does throw the necessary smokes and nades for you to be successful with a shotgun if no T's come ladder. When your team does this, you succeed consistently because of good coordination and teamplay. When your team doesn't do this, you'll only succeed if you happen to pick those rounds in which terrorists are going to ladder room. You won't be winning from skill, coordination, or game sense, but because of sheer luck. Not only will this make people angry, but it won't help you become a better player or find more success in the future.
Secondly, I'm not attempting to excuse the behavior of the players that react to what I mentioned above with anger or something similar. These people contribute to a toxic community, and in most cases CSGO would probably be a more fun game without them. But they are not yelling because they are bored or enjoy doing so; They are yelling for a somewhat understandable reason.
I didn't think other answers went enough into detail about why each gun was generally considered "nooby", so I am elaborating on that specific aspect of the question.
The p90 is commonly considered a noob gun because it has a lot of bullets and a good firerate, so you can land usually land enough bullets for a kill without really knowing spray control, and while running. Its the "noob staple" gun because people use it as a crutch for lack of spray control, and lack of ability to stop before shooting, and some bad people get salty when they get killed by people they think are using a crutch. The p90 is definitely the least situationally relevant of the "noob guns" in higher levels of play. Its not good vs ecos because the kill reward sucks and its expensive, and good players can use a famas or galil at longer ranges if they need a gun in that price range.
It's situationally useful if you are a CT and have a lot of money and want to hold down certain positions really effectively, such as B-apts on mirage. Outside of that, it is considered "nooby" because it 2 shots to the body and you can just spam it like a turret, don't have to worry about hitting individual shots as much, so people will take it and just sit still somewhere. It's considered overpowered at lower levels of skill because you can easily hold down an angle vs players who don't know how to counter you. Not used as often against good players since it can be countered by a good AWPer or trade-fragging.
Definitely the least "nooby" of your listed weapons, and also the most situationally relevant at higher levels of play. Sometimes used by noobs in all situations who hope to score easy kills around corners, but if you just use it in the situations it's meant for (areas on the map with close angles like apts on Inferno), its not a noob weapon.
There are two reason is CS:GO (and just CS). Both are because people blame others in their own weaknesses:
AUG/SG are a bit more expensive than AK/M4 so you often can't afford it. You don't have to be genious to understand that if you want to play with this gun then just do an "eco round" and don't waste all the money you have but this idea is way too complex for most of CS:GO players. Also in the CS usual game mode "Defusal scenario" once you die you have to stay dead for several minutes, not playing, not having fun -- imagine you finally respawn with a wish to buy AUG/SG but you lack $100, get killed by this gun within 30 seconds and have to wait again. This game mechanic makes people who lack skill of money management hate themselves so they start blaming you in chat. Same about SCAR because you have low chances to pick it up from the enemy so you have to collect on your own.
Another reason is more common and can be found in many games. Most of players are "casual players" -- they don't want to learn and they love to think that the game is enough primitive, allows you to relax and does not need you to think a lot. This works against most of other players but sometimes you get defeated by someone who had lower health and/or worse DPS (damage per second) weapon -- it ruins your theory about the game and makes you hate the player that was just smarter in some specific situation.
For example, for this reason in Quake 3 and Quake Live most of players hated "ctf4" and "Space CTF" maps because it's hard to win it with only "+forward and shoot" tactic that works much better in other maps. Space CTF map was different in the way that you could see positions of all players in the game in any time -- this allowed you to apply tactic related to respawn timeouts and some others while in usual maps where there are walls around and you don't have full information about the game this tactic is barely applicable so most of players don't even know about its existence.
Also that map had jumppads that could quickly change your position and your usual idea that you can easily take a bigger gun and just block the way for enemy didn't work at all. The game demanded much faster and deeper tactical thinking than other maps so people who played it the first time were raging because their team could easily lose the CTF match while having two times more frags or higher weapon accuracy.
The Counter Strike is essentially about how much time you've spent training headshots. Another big part of this game is abuot grenades teamplay but most of players don't reach it and the only thing that matters for them is how much you are able to make a headshot with AK/M4 from the distance. Shotguns and Zeus don't work like that -- you need another sorts of skill, such as close combat ambushing that allows you to kill the whole team with one shotgun cartridge or one-shot the enemy using Zeus without need to aim for the head.
