MST3K flicks don't count.
From my library the three worst are:
Cannibal Women in the Avacado Jungle of Death (W/ Bill Mahar from Polically Incorrect)
Plan 9 From outer Space (Do I have to say more the Ed Wood)
Hercules In New York (Arnold Strong stars, looks a lot like a young Schwarzenegger except speaks a lot better english)
Wo what are the worst movies in your video library