Note: This response was a lot more long-winded than I intended to be, and does not provide a lot of quantifiable numbers that you asked for. You can probably find the numbers in the Magickapedia links I included, but my intention was to answer your question as thoroughly as possible based on a lot of gameplay experience and wiki browsing instead of going and fetching numbers for you. The [QRASER] spell mentioned below is incredibly effective because multiple Icewalls will deal damage to the same target, so while its DPS looks low on paper, it's probably the most effective "I-don't-care-what-it-is-just-kill-it-fast" spell in the game.
Force/Beam Effect (Right-click)
The highest damage per second beam is commonly known as the super steam lightning beam and has the same combination as the Thunderstorm Magick [QFQFASA] You can sacrifice a tiny bit of DPS for a few seconds of longevity by switching one lightning to arcane [QFQFASS]
If you need a crowd control and damage beam, your best options are the Cold Lightning Arcane beam [ASR+SS] against non-mages, who are able to counter this fairly easily. This works best against enemies that are already wet, as it will freeze them instead of merely chilling them.
If you need crowd control and damage against mages, try the Water Arcane beam [QS+QQQ] which will knock them back and prevent them from casting anything while you slowly kill them. Most effective when enemies are trapped by a wall so they won't be knocked out of range.
For single shot charged projectiles, use the Blizzard Ball [QRQRQRQRD] against unfrozen enemies or 5-Rock [DDDDD] against frozen enemies.
If you want to spam projectiles, Arcane Fire Rocks are quick and easy [SDF] and do a reasonable amount of damage. Add steam for more damage if you can press the keys fast enough [SDFQF] WARNING: It is highly recommended that you use magic resistance to the type of elements you are spamming - [SFE+QF] (selfcast)
Barrages are almost always more efficient to spam than to add ice and charge, and the quickest effective combo is [QRAS] which does respectable damage to most enemies and great damage to point-blank wet enemies. In general, barrages aren't very effective although they are quite fun to use.
Area Of Effect (Hold shift while right clicking)
The most effective nova is the Arcane Electric Icewall [QRASE+S/R] or Life Electric Icewall against undead [QRAWE+W/R] - WARNING: Use elemental immunity or you will suicide [SARE] (selfcast) will protect you. If you think this qualifies as a wall, not a nova even though its effects are much more nova-like than wall-like, you can use the Thunderstorm combo again [QFQFASA] with area casting. This is much less powerful, but won't kill yourself or your friends as easily.
Imbue Weapon (Hold shift while left clicking)
In general, there are only a few types of imbue that are effective. The most powerful is Arcane Electric Icewall [QRASE+S/R] mentioned above, although you need to step away from it after casting if you don't have elemental immunity or you will be hit. 5-Ice imbue [QRQRQRQRQR] is surprisingly effective in PVP as it will 1-shot wizards through many types of defenses at long range (It deals 1250 piercing physical damage) If you want a more benign AoE imbue, use Thunderstorm again [QFQFASA]
Water Volcanos [QDE] have extremely strong knockback and decent range when imbued, and create a barrier between yourself and the target, making them a reasonable panic-defense mechanism.
Once again, the Arcane Electric Icewall [QRASE+S/R] does incredible damage per second in a huge area around you, but will kill you unless you are immune to it. I typically go for the final element as cold, as the crowd control is useful against a crowd of mobs, but arcane or possibly lightning deals more damage. As far as I know, it's the highest AoE damage per second in the game, limited only by your conjuring speed.
The best healing combo in the game is also a wall, Life Icewall [QWER] quite easy to remember and heals the person in the center for 6000 when AoE cast.
Volcanoes and Water Volcanoes [FDE+DD] and [QDE+DD] are quick to cast and make good barriers as they discourage foes from getting close to them to break them.
I don't have much personal experience here, but based on knowledge of damage modifiers, my guess would be [QFQFQFEA], dropping one steam element for cold if you really want it to slow down enemies as well. The above combo without the shield happens to be the best spray as well, although it's not particularly effective.
The ever-popular [ARSE] mines, made famous by TotalBiscuit and the Yogscast, great for being an arse to friends and enemies alike.
The two most popular are [SARE] and [SAFE], both protecting against arcane and lightning (the most dangerous elements) with the former giving cold resistance because of its annoying status effect and the latter blocking another common damage element. Against skilled wizards, you will often want to trade out lightning immunity for steam and water immunity [QFQSE], as those attacks deal fair damage as well and get you wet - which makes it difficult to retaliate.
ADVANCED: Currently (As of Jan 31, 2012) it is possible to have immunity to both lightning and water although they are opposite elements. This is done by combining the water with either ice or fire to make steam, which can coexist with lightning, then reverting it back to water with the opposite of ice or fire you used earlier as the last element conjured. For example, [QFAER] makes Steam, Lightning, Shield, then the cold cancels the fire in steam leaving you with Water, Lightning, Shield. You cannot conjure another element after the cancel or the game will detect and eliminate your opposite pair of Water and Lightning. The most versatile shield of this type is [QFQFASER] Which grants Steam, Water, Arcane, and Lightning immunity. Why would this be useful? You can, for instance, conjure up a Thunderstorm [QFQFASA] magick and be completely immune to its effects while spamming Arcane Steam Rocks [SD] everywhere.
P.S. Try this in the elemental section of Niflheim - The rain will instantly turn them all into water elementals, and the lightning strikes will instantly kill them.
For pure physical damage resistance, Super Rock Armor [EDDDD] works best (for instance, if your enemy is infatuated with throwing 5-rock charged projectiles at you) although it slows down your wizard considerably. It is recommended to have Haste always up if you are using this armor.
ADVANCED: A gimmicky bug allows certain Ice-Rock Armors to deal damage on contact with enemies if the wizard is moving fast enough. You will need at least 2 of these 3 speed boost effects active: Ninja Robes, Haste Magick, Knife of Counter-Striking. The most damaging combo is [QRQRQRDE] (selfcast) which appears to deal 2000 damage every half second on contact with enemies. I think this bug hasn't been patched as of the above date, but I haven't used it recently, so I'm not certain.
EDIT: Still not patched as of Jan 31, 2012
Other stuff which is fairly useful to know
Generally, while you can get a slight increase in damage by adding another arcane or lightning element to a 4-element spell, it's better to go with Cold instead as it allows you time to prepare your follow up if some enemies don't die.
Thunderbolt magick is the single highest DPS (other than Vortex, but that's an instagib) combo against any single target outdoors. being able to mas [QFASA] helps quite a bit, especially as many top-damage regular spells include it [QFQFASA] - Which really shouldn't be cast as a magick unless you have at least lightning and preferably also lightning immunity.
[QRASER] Is incredibly potent, but be wary of using it unless you have [SARE] immunity. I try to avoid using it in adventure modes as much as possible as I think it's gamebreaking and makes things less fun.
Nullify [SE] magick is great when fighting against other wizards - it will get rid of any active spells and mess up their current queueing order as well. Most useful to clear an enemy's barrier/immunity/shield before launching an attack of your own.
Cute way to 1-shot anything after you have Summon Death Magick
- Stand near enemy.
- Summon Death.
- Wait for him to corporealize.
- Teleport away.
Watch as his scythe kills whatever was next to you.
Magickapedia - The link from the other answer is broken. For some reason their site content is all still there, but has to be accessed through /index.php?title="PageName"
Various discussions of PVP and spellcasting on Paradox Forums
(Link deleted because this is my first post and there is a limit to hyperlinks - just google Paradox Magicka Forum and you can find it easily)
And a lot of my own experience playing the game. According to Steam I have 70 hours played.