Most would probably find The Loved One (1965) to be pretty horrible - at least from a good taste point of view. But a movie in which Jonathan Winters plays multiple roles is worth checking out. Also in the cast: Milton Berle, John Gielgud, Liberace, Rod Steiger, among many others. From IMDb: If you are disturbed or offended by the funeral business, death in general, dead pets, or slightly veiled hints at necrophilia then you might want to give this one a miss. If you're brave and open-minded, however, I highly recommend this truly strange and wonderful film.
A classic bad movie. ;-)