The shit that creeps me out is when you've been through a lot of baddies, scary inhuman ones and are left alone in cramped quarters(example:a hallway you fell into from above, closed on one side with one way to go and you know the beasties heard you fall and know where you are) there is bad visabily, say fog or darkness with only a flickering, dying flashlight to see with. There are several large, concealed hiding places ahead for the night lurkers and you just know it. As you take your first step a creepy violin and/or slightly off little girls singing slowly fades in, building with hints of something larger and scarier in the music as well. That kind of thing scares the piss out of me