The Profeesional is one of my favorite movies. I have liked it since I was a child.(Don't know WHY I was watching it as a kid, but I watched it all of the time)
Another one of my favorites.
I think the movie that stuck with me the longest was Dead Girl.(Not THE Dead Girl)
http://www.imdb.com/title/tt0896534/
I just found it very disturbing and was in a funk because of it all day. I don't really ever want to see it again.