I've got several, in increasing order of scariness:
The third Scarecrow scene from
Batman: Arkham Asylum, for all the obvious reasons.
The part on (I think) the ninth level of
Dead Space, when you're riding the elevator through the level's main shaft and suddenly the power freezes; the elevator entrace is covered in debris, but you can just make out something behind it...and then, it dawns on you:
"I've seen that face somewhere..." And it's just...standing there. Watching, waiting...and then it slowly lopes away, as if its only purpose was to let you know that it has been freed, and wants your blood. I still have nightmares about that scene.
A bit in
Bioshock, shortly after the part with the exploding submarine. As I was walking back to the (relative) surface, I saw a narrow, secluded pathway, lined with pools and leaky pipes. Letting my curiosity get the better of me, I readied my wrench and walked down the passage. Inside, I found some kind of shrine, where A book, several pictures, and a Raggedy Anne doll had been surrounded with candles. I studied it for a moment, conscious of a heavy breathing sound I deemed to be the pipes; I turned around, and then not a single foot behind me, was a Houdini splicer. He didn't attack me, taunt me, or so much as acknowledge that I was looking back into his mask's eyeholes. He just...
looked at me, before abruptly vanishing, never to be seen again.
I shat myself.
Try topping those.
