ArmA II with the DayZ mod for the PC... Zombie survival, open world with dozens of players, you start with nothing but the sound of wind, a pistol, and your buddies. If you want a map, you find one, if you want a compass, you find one, if you want live, you must be quiet, as your voice is heard in proximity. And theirs a full night sequence in every day, no light whatsoever. Its terrifying.