For me, it has to be mystery. I can cope with any deal of graphic and disturbing violence in movies, and I don't find monstrous creatures in the least bit frightening - other than those cave crawlers in "The Descent", or people in a state of possession ("The Exorcist" goes without saying...even if I just said it) or the similar process of being infected with something (see the movie "[rec]" for a much clearer explanation of why it's so damn creepy). Japanese ghosts and strange disturbing sounds and images from movies like "The Grudge" or "The Ring" (ugh...don't get me started on that goddamn movie!) probably scare me the most though. But what puts me in a state of unease more than anything else mysterious things that are never explained.
Like all the scenes in "The Blair Witch Project" where we don't actually see what is happening to these people but we're able to hear and understand that it's pretty damn freaky, or the scenes in "The Shining" such as Kubrick's strange mysterious and rather Lynchian fixation on room 237 of the hotel they're in. Another great example of this is the scenes in, as well as the general overtone of, Peter Weir's "Picnic at Hanging Rock"; where we just see these three girls almost possessed as they wander further and further into this strange place, while the other girl (and the audience) has no idea what the hell is going on with them.
What are other people's thoughts, and what do you find the most scary in movies?
