The Exorcist III from 1990 starring George C Scott is one of my favorite movies. It was directed by William Peter Blatty, author of the original Exorcist novel, and is based on another novel of his, Legion. It's a very deliberately paced, tension-saturated film. It didn't review very well because it was not intended to be an "Exorcist" movie (Legion was not part of the Exorcist canon) but the studio pressured him to fit it in, so they actual exorcism climax feels a little tacked-on.
If you can forgive that though, you're treated to a very moody, very tense story that is excellently written with strategically well-placed scares.