Ok I saw a movie when I was younger made in like the late 80's early 90's. From what I remember the guy gets possessed somehow by a demon but he's in love with this girl. A few scenes are she goes to his house and as a joke he explodes his head freaking her out but its humor, a woman steals a dagger from some collection to try and kill him but in the end he's freed and instead this poor guy gets possessed and I think the closing scene the guy winks at some chick and flirts.

Check out "my demon lover" with the guy from family ties