Tell which game should I beat

I put myself an objective: I have to beat all my steam games just because.
So I will let you choose which game should I beat first. (Choose a game that actually has a singleplayer mode that can be beaten)

As you can see in my profile there's a list of the steam games that I have already beaten.

Choose wisely, and please do not choose F2P

P.S.: In this moment I am playing BioShock.
P.S.2: Please mods, don't close the post. I will be beating the games and updating the post

Queue:

Bioshock -- Beaten!
Orcs Must Die! -- Installed
GTA:SA -- ...
Metro 2033 -- Playing
Uplink -- ...
Defcon -- ...
VVVVVV -- Beaten!
The Witcher -- ...
Amnesia: The Dark Descent -- ...
Supreme Ruler Cold War -- ...
Super Meat Boy -- ...
Dungeons of Dredmor -- ...
Darwinia -- ...
GTA 3 -- ...
Borderlands -- Installed
Psychonauts -- ...
The Revenge of the Titans -- ...
GTA:VC -- ...