What are your top ten favorite first-person shooters?

[Reasonable]

I know this isn't 10 but this is how I think of FPS ish titles:

SP

1 - Half Life 2
2 - Half Life
3 - Doom / Doom 2
4 - CoD4
5 - Halo CE (PC)

MP

1 - Unreal Tournament
2 - Unreal 2 XMP
3 - Day of Defeat
4 - Team Fortress 2
5 - Counter Strike Source

FPS Hybrids

1 - Deus Ex
2 - System Shock 2
3 - Stalker : Shadow of Chernobyl
4 - Bioshock
5 - System Shock


Honorable mentions for FPS I've played and liked a lot (no particular order here):

FEAR

Doom3

Serious Sam

Painkiller

Resistance 1 & 2

Halo 2 & 3

Killzone 2

Shadow Warrior

Duke Nukem

Battlefield 2

Mirrors Edge