Zandronum

Felt like reviving this thread.

SCP - Containment Breach is a free survival-horror game based on the SCP Foundation (which is a collection of "data" on fictional paranormal things and other eldritch abominations).

You're just some poor sap working in the facility, when, holy shit, the power goes down for just a short ammount of time and one of those SCP's makes things just simply mess up terribly. Oh, and there's also a bunch of other bastards like 173 out there in the dark.

You have to survive in the facility and need to escape from there. Damn atmospheric game, still under development, but pretty sweet.
Homepage for the game

Some videos and whatnot related to the game.

Main "baddie" (SCP-173) in a short video Now that would suck to die like in real life (spoilers gameplay a bit) Some dude playing the game

lol I played this, then I played Slender. Both are equally scary. Both need to have infinite running though. Walking is annoying.

Another Video:

I've seen some let's plays of it, tho jumpscare horrors aren't my genre. I'm too nervous for them. I prefer rather some light horrors with good climatic (but not so disturbing) music. Ib (it's name of a game) for example, or, w/e, Doom 3 (didn't played both of them tho, seen Ib let's play and some Doom 3 parts).

Game seems to be excellent tho.