My favorite obscure movie is "The World's Greatest Sinner", made in the early sixties with a soundtrack by Frank Zappa.
This one is insane. It's really pretty lousy, but it's also just about the greatest movie I've ever seen. It was written and directed by some two-bit actor, and he also starred in it.
The plot is about a salesman who leaves his job, starts a really gross band and declares himself to be god.
It's insane. And I mean really, actually insane.
Here's the world's greatest sinner's band in action.