I find the best horror elements are those that make the viewer feel uncomfortable or ill at ease, rather than outright scared.
-Moving scenery is pretty effective, especially if it only moves when you aren't looking. It ruins any sense of familiarity with your environment, and creates an element of distrust between the player and the game. Even if the scenery never actually does anything, its hard to trust "inanimate" objects that won't sit still.
-Weird angles and geometries. Nothing too crazy or out there, just shy away from right angles in your architecture. You can create some effectively creepy shadows this way, as well as just make things look off. Playing with the sense of scale can do this as well, if just to make the player feel uncomfortable.
-Ambient noise. Not necessarily music, just random soundbites that prelude something bad happening. The air raid siren and radio static in Silent Hill is a good example. It's something *familiar* that, in a new context, becomes unearthly and creepy. I'd usually refrain from saying good things about it, but the Tom Cruise version of The War of the Worlds had an EXTREMELY effective version with the noise the Striders made. Ditto the mooing that the Metal Gears in MGS4 did. Taking a familiar and "safe" sound and making it not so goes a long way towards catching the player wrong-footed.
-Reviving monsters. Not the traditional "walk off screen they come back" kind, but randomly regenerating ones. Especially if it truly is random, and a respawned version is more dangerous than the original. The Crimson Heads in the RE1 remake were fantastic in this regard: you couldn't even trust your weapons. If you killed a zombie wrong, there was a chance that it would come back as a stronger, faster version that would hunt you down. This puts another element of discomfort in the player's mind. "Did I actually kill that one? Is he playing dead? How do I tell? Do I have the time or resources to be thorough every time?" etc. This works better than making the combat hard/bad/clunky/whatever. Let the player trust their own skill, just make them worry if it's enough.
-Don't explain things! The scariest parts of a horror story are when the characters, and the viewer, don't know whats going on. Giving an origin or cause to something grounds it in reality, and gives it a finite existance. "Anything that can be made can be unmade", in other words. It's one thing if the dead have risen and are killing the living for no reason. It's another when you realize that its just a contracted disease and you can avoid it by avoiding zombies and washing your hands and shit. Suddenly your unstoppable force becomes no more terrifying than a common cold. Albiet meaner. I thought that The Thing was a good example of this. The monster is never given an origin, or a reason for what it does. It simply "is". And if it gets you, thats it. You can't even tell who has been infected, without a lot of research. Added to the truly alien way it goes about its buisness, and its some pretty scary shit.
Sean Hollyman said:
So what would you put in a game to make it truly scary?
I'd put something in there that follows you wherever you go. You can't attack it, but it can attack you, and it walks really slowly, but doesn't stop. But it's there. It's always there. Wherever you go.
This is a pretty good one, reminds me of the Friday the 13th series. Especially if it was a game with a heavy exploration focus. The player would have to make a concious choice to hang back and explore, and risk the monster catching up to them. It gets rid of the safety that comes with having "cleared" an area, by forcing you to move on rather than catch your breath.
