Borderlands

HOLY MOLEY THIS GAME IS AWESOME.

Seriously, I bought it at $39 bucks a few months back and wasn't seriously expecting too much but was instantly blown away. The game requires a lot of teamwork. Although you can solo the game, the true enjoyment of the game comes by usually playing it with your close friends. The storyline is subpar, but the gameplay is more than enough to make up for it. Now at almost half the price I bought it for. Definitely worth the 20. message me and tell me your preferred meet-up location if you have one.

http://en.wikipedia.org/wiki/Borderlands_(video_game)