most fun PC online (non-mmorpg) multiplayer game?

I'm seriously thinking of getting Team Fortress 2.
how is that game? i used to play the first game, and i enjoyed it.

what are some other fun multiplayer games?

Teamfortress 2 is crazy fun

^ prolly right

DOTA

dude, i got TF2 and it's not THAT fun... fuck. the spy was my favorite class in TFC but the spy is fucked in this version because you can run through your teammates but can't with enemies, so it's so easy to discover spies. Furthermore, MOTHERFUCKIUNG PYROS make life hell for spies