Amnesia: The Dark Descent hands down the scariest horror game i have EVER played. I have had nearly every horror game made since 1998 and Amnesia nearly made me piss myself on more than one occasion. More than i can say for almost every horror game i have played. I believe it sells for around 20 bucks on steam or on mac it is in the app store. The game last for around 15 hours or so. If you get it on steam you can download user created storylines after you beat the game.