What are your top 10 favorite single-player first-person shooters?

[Severance]

CollectiveCynic said:

Basically what the title asks.

Here is mine:

Deus Ex

Half-Life Tied with Half-Life 2

System Shock 2

Doom

Halo: Combat Evolved (Haters gonna hate..... That is the last time I'm saying that)  plus 2

No One Lives Forever 2 plus 1

Duke Nukem 3D

the ones you listed here PLUS

Every james bond FPS

Medal Of Honor Frontlines / Underground

Quake (All ID software games actually)

does Portal count?

Rainbow Six (the PS1 ones)