It's really hard to choose! A dear departed friend of mine & I used to torture each other with bad movies...I started the ball rolling with..."Billy Jack"...she was quite a few years younger than me so I ALMOST had her convinced that "Billy Jack" was a truly great film, one of my formative influences...hehe :)
She countered with "Karate Kid, part 2"
My reply? "Plan 9 from Outer Space". That particular film is at the top of many "worst" lists...
She tormented me with "Conan the Barbarian"
My next move? "Children of the Corn"