The unexpected. Games like FEAR (especially the second game) and Dead Space do it perfectly.

FEAR:
In FEAR, there were times when you'd see or bump into Alma when you least expect it, and then shit a brick. There's one part of the game when you're going through a crawlspace, and your torch stops working so your character looks down to try and fix it. When it works again, you look back up, and Alma's face is right there infront of you.

Sometimes you'll just be running around after a gun fight for some ammo, and she'll be right behind you - you'll either catch a reflection off of something and see her just looking up at you, or you'll turn around 180 degrees and walk right into her.


Soundtrack helps. Music with a sudden start that smashes through silence is a good way to make your audience jump. In Dead Space, you'll be walking quietly down a hall and then "BAM!" something will break through the ceiling at you with the trademark "screech/nails down a chalkboard" sound.

Video of the very first level: Spoilers?



In terms of music... this really gives me the fecking creeps.

Weapon/ammo rarity is also pretty scary. When I was playing Dead Space on the hardest mode, there were times when I was completely out of ammo, so I'd be holding my breath and hoping I'd find some before the next necromorph came at me.