The "Maniac Cop" Trilogy.
Despite having an incredibly goofy sounding name, the movies are very satisfying and enjoyable. They constantly flip flop between genuine suspense, intrigue and drama to cheesy fun, yet it never becomes jarring or shatters the mood. All 3 movies are a blast, and manage to stay engrossing and fresh throughout the whole series, which is a rare feat for a slasher film.
Oh, and both the 2nd and 3rd movies feature gloriously badass finales involving Cordell (the titular 'Maniac Cop) being fully functional while completely enveloped in flames. For extended periods of time.
Then again, this could always be less a "Great Movie (series) That Nobody Has Seen" and more of an "Obscure Guilty Pleasure", but who cares? I personally find them to be more fun than a barrel of monkeys.
Oh, and another shout out to Session 9. Being a jaded, long time horror fan, I'm finding that nothing is really that scary to me anymore. Session 9 displayed a mastery of the genre, and took pride of it's understanding that all you need to do is get the viewer to scare themselves. It was intensely atmospheric, and there was a very heavy uneasiness pervading every scene. It's definitely the type of film you'd want to watch alone in the dark in order to get the full effect, but the full effect is a very satisfying and disturbing experience that you won't forget long after you turn the movie off.
