I have trouble with this, because unless they fall into the “laughably awful” category, where the pleasure is strictly in making fun of them (like “Plan 9,” “Creeping Terror” or “Showgirls”), if I like them, I don’t think they’re horrible.
One possible exception might be “Hold On,” starring Herman’s Hermits. Amazingly stupid storyline and prime example of 60s silliness, but it’s fun to see the band in action.
I suppose the beach movies also fall into this category, especially since I find most anything with Buster Keaton in it worth a look.
Then there's this one:
I'm glad I found a soulmate. :-)
A bunch of college guys under a rug posing as an ET gobbling up people. Horrible acting, ludicrous monster, a spaceship full of WWII electronics - but what got me was the premise: Aliens send a device to another planet to sample the local flora/fauna/what-have-you - and report the composition.
Just like one of our Martian probes years later.