Recommend Me A Good First Person Shooter.

BioShock, Battlefield 3

Unreal Tournament!

Also Bioshock, TF2, Left 4 Dead, etc.

Battlefield 3 < THE BEST ONE EVAR!
In Steam? Hrmmmmmm Battlefield 2, CSS, Half Life 1/2

CS:GO

Half-Life 1

UT99

Far Cry!

HL2 and Borderlands. Both of them.

Prey.

fortix

Natural Selection 2

dude, team fortress 2. if you're letting all the hoopla put you off, dont. its solid.

Counter Strike.

wolfenstein 3d

Life itself is a great FPS so i heard.

Blacklight Retribution.

Duty Calls. 'nuff said.

Sanctum! Not enough people give it credit as an FPS, since it's also a tower defense game. But dangit, it is amazing.

Team Fortress 2, Tribes: Ascend, Ace of Spades. All are free and amazing. Oh, and there's Sanctum, but that's a hybrid, so.

hard reset! great game!

Ace Of Spades its a pixelated FPS where you can build and destroy terrain :D and shoot people, and shoot terrain

DOOM II + Brutal DOOM mod

Singularity.

If Bioshock and cod had a baby. This would be it.

Great story/gameplay.

Fallout 3, Fallout new Vegas, these are RPG's but still fps'

COD MW3. It was the Game of the Year of 2011. Trust me. :D