What is the scariest game you've ever played?

So I love horror games. Amnesia, Resident Evil, dead space, etc I love em. I've never played a Silent Hill game. So I picked up the SH2 remake and Holy shit. My butthole has not unclenched since playing. It's pure tension the entire time.

So! What sort of games have you played that are truly nerve-wracking and give you the heebiest of jeebies?