There are lots, depending on what your definition of "horror" is... and are probably the best haunting/possession-types; , , and are my favourite violent slasher-types (although the sequels to those are almost all pretty terrible, with a couple of exceptions); some people consider and to be horror, and they're two of my favourite films... and that one scene (you'll know it if you've seen it) in the original Japanese actually scared me so much it felt as though something broke slightly in my brain, and I've not managed to bring myself to rewatch it yet. I wouldn't call it my favourite
horror movie, but it certainly bothered me the most.
But overall I think my favourite has to be (and I'm not talking about the Nic Cage version
) because it's just so unique and unsettling and the ending is one of the very best things ever put on film, ever (and Christopher Lee, who is absolutely brilliant in just about everything he's ever been in, gives probably the best performance of his career).
(Which version of Dawn of the Dead
did you mean, Till? I love the old Romero movies and I've heard surprisingly good things about the remake, but the fact that it's made by Zack Synder really puts me off seeing it.)
In a similar vein: your favourite Western?