Amnesia for sure! I was actually too nervous to continue playing, because I sat and played it in the dark, with headphones, alone.
http://www.multiplayerreviews.com/gamepage?id=862&game=Amnesia_The_Dark_Descent&review=1
http://www.multiplayerreviews.com/gamepage?id=862&game=Amnesia_The_Dark_Descent&review=1