Battlefield 3 is a good FPS game with a not bad SP mode but an even better MP mode.
Crysis 1 and Crysis Warhead are two others.
You've got a GTS 450 right?
yes. i enjoy playing on GTS 450 and phenom 550 combination.
crysis 2 was great and now i am thinking of playing crysis and company of heroes for great single player fun.