are portal and Mirrors Edge really FPSes? i find them more of a Platformer (Mirror's Edge) and a Puzzler (Portal)
i don't they're "Shooters" ya know?
You're always in first person, and almost always have a gun... which you shoot with, constantly. There, that's my justification :p
Mirror's Edge would've made my list, but that has hardly any shooting in it, so I left it off.