The three classes most suited for killing Snipers are:
- Snipers. Some maps in particular are very Sniper-battle friendly at the beginning. Most payload maps are a good example (see: pl_goldrush stage 1, pl_badwater, pl_upward). Pretty much all maps are sniper battle friendly in the middle.
- Spies. Even with a Razorback, a Spy can just shoot you 3 times (twice with the Ambassador, assuming the first shot is a headshot) to kill you.
- You wouldn't think Scouts would be, but it's easier for them to get past Snipers due to their speed.
Now, due to the new weapons added into the game last update, there is now one more class that is ridiculously overpowered versus Snipers. That is... the Heavy with the Fists of Steel out. Simply put, a headshot will no longer kill a Heavy who has the Fists of Steel out.
A fully charged rifle headshot does 450 damage. Reduced 60% is only 180 damage.
Note: That's FULLY CHARGED headshots. A "zoom and boom" headshot only does 150 damage normal, or 60 damage versus a Heavy with Fists of Steel.
Oh, and it appears that the damage rate is currently messed up for this, as when I was playing Heavy, zoom and booms were only doing 40 damage. You could tell it was a headshot because it did the critical hit sound.
Basically, what this means is that a Sniper has no real ranged way of dealing with a Fists of Steel Heavy, not that will kill him before he crosses the open area... which means he can get behind the Sniper and mow him down with the minigun.
Of course, the best defense as a Sniper against this is Jarate plus Bushwacka, which will one-shot a Fists of Steel Heavy.