Best FPS game you have played

Darkness 2

No good at picking favorites like that, especially a single one. Going more by playtime, I could say Borderlands. Thinking back to untracked times, Half Life and Unreal Tournament.

Natural Selection 2

Singleplayer: Half-Life 2

Multiplayer: Battlefield 1942

:)

half-life 2

Serious Sam: First Encounter

Goldeneye, TF2, CoD4

In no particular order :)

Half-Life 2
Practically, every game from the Half-Life series.

I do believe no one will "upvote" this post, but:
Metroid Prime

Wolfenstein 3D. /thread

System Shock 2.

I guess the last shooter I actually enjoyed was Unreal Tournament. Anything after that always felt like more of the same.
I guess the genre isn't my main gaming appeal.

SKYRIM, because people say DX:HR... morons..

Seriously now, I think CS 1.6. Spent a LOT of time in it, got some epic memories.
As for shooters in general, Gears of War. Also had a lot of fun there.

Single player: Half-life series

Multiplayer: UT2004

TF2!

Battlefield 3

007 Goldeneye
BF1942
UT99
and Half life series + mods

Killing Floor ftw !

BF3

Bioshock and Clive Barker's Jericho D:

TF2

CS 1.6

Q3,UT series,KF

Action Quake 2. Classics will be classics. I believe Action Quake 2 was, in some way, an inspiration to Counterstrike.

And more recently, Battlefield 3. This game is just so damn immersive... and HUGE!

Quake 1.