Borderlands is a hell of a game, and you can usually find the Game of the Year edition (with all the DLC packs) for something like $30 new these days.

Meier mentioned Red Dead, which I fully support, as I just beat the PS3 version a couple days ago, and it's pretty damn great.

Also, you can rely on the classics, like 50 Cent: Blood on the Sand, and if you can find it, Deadly Premonition. Both of these games are amazing and anyone who thinks otherwise is a god damn communist.