1. Fallout: New Vegas
2. Deus Ex: Human Revolution
3. Fallout 3
4. Bioshock
5. Call of Duty 4
6. Borderlands
Not that big on multiplayer shooters, and I don't have a PS3/Gaming quality PC, so my list is pretty limited. There's some other stuff that I enjoyed a little bit, but not really enough to put on a list (Battlefield 3, Fear.)
I definitely wouldn't call FO3/NV or Deus Ex FPS' (Borderlands is kind of iffy too but I guess I can see it). Unless we're using the barebones definition of FPS.
Anyway, TF2 and HL2+Episodes are great answers here.
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Will not remove this line of my signature until the Seahawks, Jazz or Rockies win a title (Started 5-16-09)
SuperNiceDog: Guru winner