Siren Blood curse
Seriously, if you think Minecraft, Fallout 3, Amnesia, Eternal Darkness, Bioshock, and Dead Space is scary, you haven't seen nothing like this game.
Also project zero (fatal frame) 2 crimson Butterfly. Ghosts coming out of nowhere and scarring the living shit out of you, fuck this game, i couldn't even play it for more than five minutes without shitting bricks in my pants.
You can have your monsters, and abominations, and blood dripping on the walls, but you can never beat a bunch of ghosts in the "making you piss yourself scared!" factor.