Wow, glad to see all the results so close!
As for my vote, I am in the same boat as Mark (as usual
). Sleepaway Camp rules the roost, with Friday a close second. In Friday the 13th you could kind of see it coming...with the open shot of the girl in the lake and the upbeat music, but in SC it all came out at you before you really had any time to contemplate it.
It is a tough pick though, I really like all the endings!
As far as The Sixth Sense...it was either that or COS, and since (SPOILER) COS did that ending more than 40 years before Sixth Sense, I thought it deserved the recognition.