Battlefield Vietnam and/or Battlefield 1942 are great.
RTC Wolfenstein: Enemy Territory is great ... and its free
Call of Duty is very good, though I prever the games mentioned above better (though the single player in COD is among the best I have ever seen)
I didn't like the Demo for Far Cry all that much, but a couple of buddies at work rave about how great the game is, so I will likely purchase it.
I tried dues ex 2, and hated it, I couldn't figure out how to turn off mouse smoothing or mouse filtering or whatever its called, and I im extremely intolerant of mouse smoothing.
I played the Demo for painkiller, and I thought it was the coolest looking game I had ever seen, the physics in that game are freiking amazing. I haven't played the full version yet ... but it is on my list of games to acquire.