What makes something scary

[Kurton]

Also, since I bet a lot of people are attuned as to which sound effects imply danger, and which are merely for cosmetic/aesthetic effect, and if you had some nice audio software, you might make your own scary "what-the-hell-was-that" effects for some refreshing surprise (and that extra bit of artistic license. ;) )

[xtron]

For me it's the frustration. Like the water part in The Dark Descent when you need to open the damn door and it takes like 10years and all you hear is the damn water lurker coming upp close...I can't handle that part without my heart beating 200beats/sec.

[GraphicsKid]

The most general answer I can come up with is this: things are scary when there's something unknown in a situation and the player's imagination is forced to come up with something.

For example: A long dark hallway is scary because we can't see what's down there, so we start thinking about what could be down there. Or what if there were a pair of glowing eyes at the end of the hallways? Now the player knows something is down there, but doesn't know what. It's probably not something pleasant!

I remember during my first few play-throughs, the monster sounds (not even the monsters, just the random sounds it'd play, like in the archives) were really scary because I hadn't yet seen what the monster looked like. I was forced to imagine something, and your imagination can always come up with something more frightening that what is put up on the screen.