Amnesia the Dark Descent
I've always been a fan of the survival horror genre even when I was just a kid, but to tell you the truth, the only series that I actually found scary was the Silent Hill series. But lately that seems to be lacking in the game industry. Amnesia however does its survival horror in a way similar to Silent Hill, but they take it further and it makes for an experience that makes you wanna shit yourself.
It's all in first person and there isn't really any way to fight back against whatever the hell keeps trying to kill you in this game, and if you do get close enough to one of these things to get a good look at them, your probably as good as dead. The main focus of this game is immersion, which I think Frictional has done damn well on in my humble opinion, the way you interact with the environment, I actually kind of feel like I'm the one digging through drawers and hiding in the dark from things that go bump in the night.
All and all, I've yet to finish the game myself (school and all) but I recommend this one to any horror fan. You can pick it up for about $20 or so off of steam or Frictional's website.
Frictional Games