To anyone that liked Exorcist 3, I urge you to check out the Ninth Configuration. Like I said earlier, it's from the same writer and Director, and in my opinion it's one of the best psychological thriller/horror movies i've ever seen. Also, as you watch it, it'll become very clear what popular recent movie was heavily inspired by this.
Here it is in full. Might not be up for very long so I figured i'd share it now with the fine Folks on WF
It's a slow burn, and it's a weird movie. If those two things don't bother you too much, you're in for something special. Almost starts off like a more fucked up One Flew over the Cuckoo's Nest, but evolves into something much darker and suspenseful if you give it the chance. There's some really interesting dialogue in the movie concerning the belief in God vs the non-belief, but that's expected from William Blatty.