For my birthday I got a good sum of money, and I decided to spend some of it on a new Steam game.
Games I already own:
BioShock
BioShock 2
Garry's Mod
Left 4 Dead
Team Fortress 2
Counter-Strike: Source (Though I don't like it so I'm not getting any other CS games if they exist)
Half-Life
Osmos
Portal (hurr)
World of Goo
(I know, seems like I'd be content with what I have)
I was thinking maybe L4D2 or HL2 (even though I own the latter, but for Xbox), but those are just little thoughts.
I prefer action and adventure games, though RPG is fine too. If there's a demo of the game it would be even better.