1. Call of Juarez: Bound in Blood
2. Blazblue
3. Halo 3
4. Fight Night Round 4
I'd recommend all of them, except Fight Night Round 4. For some reason that game continues to piss me off, but I keep trying to give it a chance. I loved FNR3 but can't seem to even enjoy this one.
Call of Juarez is really cheap on Amazon right now @ $35, Gamestop is going to have it next week for $40. It's really worth your time if you enjoy FPS and Westerns.
Halo 3 is a game that I always refused to play just on principle, but I'm actually enjoying it now that all of the hype has died down. The graphics are silky smooth, and the controls are spot on. I still think CoD4 owns the pants off of it though.
BlazBlue is one fantastic fighting game. If you like fighters you should really pick it up - and Street Fighter IV - if you don't have it already.