Films that are so bad they're good

I've just read a review of a new film called "See you soon" which the critic describes as being hilariously awful. I started thinking about bad films that I've enjoyed and remembered "Beyond the Valley of the Dolls" which we saw many times. It was often on at the NFT where most of the audience had also seen it more than once and who anticipated the "funniest" lines.

I'm interested to learn which bad films Gransnetters have really enjoyed.