I have played many horror games over the years and games with horror elements in it. Ravenholm in Half Life 2 still gives me the creeps (especially with the cinematic mod's visual overhaul). Resident Evil 4 is still one of the greatest horror adventure games ever made. The Metro games had some great horror moments. Hell, even Starcraft 2's zombie map scared me (An RTS that managed to pull off a horror moment, that is an accomplishment). However, one moment in gaming continues to 'haunt' me. A moment that is etched in my mind. That moment, came from F.E.A.R.
The first mission, Inception, has you searching for Paxton Fettel. Well, as I search for him, and have to endure an oppressively creepy atmosphere, I get to a door, and just as I am about to open it, here come Paxton to walking past like a zombie. I nearly jumped out of my seat. It was just so perfectly timed, the sound effect, everything before hand, like finding that mutiliated body prior, that it became the talked about scene when I discussed it with my friends later on. The rest of the game was a tour de force of horror action, but still, that scene remains the thing I remember the most about it.