[Sirius]

I purchased Counter Strike: Source yesterday, it's an awesome game.

[lux]

GRID 2, Make sure you have a controller handy though....

[Diego]

Killing floor is a great game! Ive been playing it lately and its so fun to get a game going with friends. When you buy the game you get two passes that allow you to send to a friend so they can play for 2 days. So if you ask around you could try the game before you buy it. Also its on sale right now for only $4.

[Oni]

A really great one to play is Garry's Mod. I've played on DarkRP servers with the other members and it's always fun!