Play Diablo series to get eerie feeling ;)

FEAR 2 was probably the scariest I've played so far.

I normally don't get scared from a game, but after playing it with both, my headset and Surround sound speakers at a very loud volume, you'll tend to get an intense feeling coming up but you just don't know when.

quake 2.. i was like 8 years old when i played it.. damn O_O

Lol

I have to agree with Fear 2 but If Gmod counts there's a couple short horror maps that are the freakiest thing I have ever seen look them up at GarrysMod.com

Also the stalker  series of games and metro 2033.

Resident Evil and the Friday the 13th on nintendo was pretty scarey when I was younger.

Dead Space, that game made me jump, once and its the only game that has done that lol.

Silent Hill for me

I would have to say the older resident evil games when they first came out

crysis, when ur in the alien cave

that part almost gave me a heart attack when those green alien things came outta nowhere screamin at ya and attackin ya

dead space is good fun.