Elements that i find work pretty well in my own writing:

1. Fear of the unknown. Revealing tiny bits of information at a time lets the reader develope their own picture of what is coming, often which is far worse than you can describe.

2. Hopelessness. I use this one a lot. In Gloom and Father Dillon's Funeral (hell, even Bearwood, come to think of it), there are parts where the characters are compeltely stuck, with no obvious way out. I am rather proud of the ending of Father Dillon's Funeral. Very Dark :)

Unexpected things can also be very effective. I always refer to loud noises as "Boo!" scares. They are a cheap (but effective) trick that pretty much all horror uses at some point. Anyone remember the scene in Aliens where there is a liong build-up of suspense hearing the motion tracker pinging, the team with Hicks, Drake, Ripley, Gorman, burke and Frost all floow it into the hall, the guys get ready and then BAM! There is a burst of motion, and Hicks sprays off a bunch of rounds from his gun. 2 seconds later, you realise it's Newt, but up until then, and when the noise hits you, it scares the piss out of you.

Another, slightly different version of this is the face in the Exorcist. usually the things that pop up and scare you are noises, but the face that they slip in for a a frame is downright frightening, and it pops out of nowhere. It is probably one of the most effective horror tricks ever used, because most of us arent even aware we saw it the first time, but it is deeply unsettling.

i am afraid of jello it is food that moves

when it happens in real life like the 9/11 aattack.. that was trrue horror to me:(

I think a lot of people are missing the point of the question. He is asking which among the common elements of horror movies really scares us the most. He is trying to figure out exactly what to put into his story.

I think i offered up some constructive info with my 1 and 2. the rest was commentary, because i love hearing myself talk and reading myself write (:confused: )

We have a lamp that refuses to turn off properly. the first time we realised we had a problem with it, we had just finished watching the Ring, and were talking about it in bed, and then the light in the living room turned on all by itself. it took me a full minute to pull myself out of bed to go check on it....

Jesus, I would have wet myself. I had a hard enough time driving home after watching that movie... at 2am. Alone. On back roads.

i saw a really creapy spider just now