Oh, I almost forgot to add The Exorcist III!!! 
I have more I could list of course, but these movies are a few that still impress me to this day.
BTW, anyone familiar with my Avatar? I can't believe no one has commented on it yet! 
I know the series, Phantasm if I'm not mistaken? Event Horizon and The Cube are favourites of mine ( though not all that scary, J-horror rules in that area:).
