personally i think that The Exorcist is hugely overated...

i'm gonna say the original texas chainsaw massacre, mainly because when you finish watching it you remember the things that never happened, such as a girl being impaled on a spike and a boy in a wheelchair being torn apart by a chainsaw, you never actually see any of those things happen, but they are done in a way that you focus on the violence and expect there to be blood so much that your mind creates that part of the film for you... remember this, even though it is known to be one of the most gory and brutal films in history, there is less than half a bucket of blood in the whole film and less than 2 minutes of brutality...

also carrie was pretty scary, especially the hand at the end, i mean you knew that it was coming but when it did it still made you jump....those are the signs of a truely AMAZING horror film...

nevertheless, my favourite has always been and will always be Evil Dead....i know that this post is not asking for favorites, but you cant have horror without Evil Dead...i mean come on... its a cult classic..