For me, it is still that scene in The Omen. That kid is trapped under the ice and he is pounding and trying to break through it to breathe....I just can't imagine and I really don't want to try. Actually that is the scene that sticks with me.
In the movie ,The Ring, I kept wondering what in the world could scare somebody so bad they would die in a frozen scream. The first time I saw that little girl crawl out of the tv, I actually fell over the back of my couch. hahahahahaha - that was the best scare ever!