I was lucky enough to see the room in the best way possible. Adult Swim was airing it on April Fools and I flipped to it. I didn't know in advance how awful it was so I got the full "wtf" experience.
Reefer Madness is a classic.
Showgirls is so bad it's good, plus Elizabeth Berkley is really hot.
Manos Hands of Fate.
And... while I'm hesitant to get into this territory, I find a lot of Christian films like God's Not Dead so awful that they're good.