Amnesia: The Dark Descent, a first person survival horror. A game about immersion, discovery and living through a nightmare. An experience that will chill you to the core.
Amnesia is probably the best horror game ever. Like, seriously, the mechanics are new and fresh and the whole interactive objects thing just makes for some hilarious gameplay. The creatures feel alive when they hunt you down, and I do love that it is possible to NOT hide and just run away from them, but you usually don't because they have great AI that really works at cornering you.