14. Portal (2007)
Portal imagined a sleeker FPS, your gun opening physics-defying doorways in a laboratory hellscape. Red and blue, up and down, the puzzles challenged the most seasoned snipers. The hilariously deadpan GLaDOS made the game as witty as it was difficult.
13. F.E.A.R. (2005)
If you watched The Ring and thought, "Man, I'd love to blast that long-haired Japanese well-dweller with a machine gun," then F.E.A.R. was the game for you. Blending elements of J-horror with traditional FPS action, F.E.A.R. was the rare game that could transition from action set-pieces to true, bowel-releasing terror.
12. Metro 2033 (2010)
Metro 2033 was a bizarrely WTF experience. Psychic powers? Check. Ghost monsters? Oh yeah. Post-apocalyptic Russian subway systems? Sure. Ammo treated as currency, so that the better guns you buy, the less you have to shoot? Weird and innovative. Metro 2033’s clever twists on shooter tropes made it a surprise from start to finish.