Cheap but good PC games?

[Robin Williams]

It was already mentioned but "Amnesia: Dark Descent" it should pretty much be a requirement for all gamers to play. It's cheap but near impossible to get a hold of unless you do it online, and doesn't have heavy replay value. Definitely a consideration though, otherwise Minecraft, and really just any RTS worth it's weight. ie. SCII AoE, AoM, WC3, etc.

 

[GeneUnit]

Check out the S.T.A.L.E.R. series, they're on steam, and some of the most atmospheric games ever, just make sure you get the complete mods. Improves graphics and gameplay and fixes bugs while leaving the story and basic game the same. http://www.moddb.com/mods/stalker-complete-2009

 

[Ikaruga33]

Platformers (free)
http://www.gamemakergames.com/archive/jumper
Hard little game

I wanna be the guy
EXTREMELY HARD AND FUNNY GAME

Shmups
Genetos
A game where you play through the evolution of shmups

 

[Yureina]

If you are into RPG's, go on Steam. You can't go wrong with Deus Ex and the first two Fallout games.