Oh man, so many. I'll try to stick to "bad" movies and not commercial flops that later found a nostalgiac audience (so no "Hook" or "Big Lebowski")
-Super Mario Bros. - Mentioned earlier, of course. I watched it when I was... I don't know, eight? And I digged how stupid it was.
-Street Fighter - Come for the memes, stay for Raul Julia hamming it up
-Jupiter Ascending & Speed Racer - I assume Speed Racer is considered a bad movie? Maybe it isn't; it definitely shouldn't be. These two films cover the Wachowski sisters' "stupid but fun" phase and I love both films dearly. This was the role that should have won Eddie Redmayne an Oscar.
-Dungeons & Dragons: Wrath of the Dragon God - Yes, it was a crappy low-budget SciFi (sorry,
SyFy ) movie. But damnit if it didn't consistently feel like Dungeons & Dragons. The Lich that the Big Bad allied with peacing out when it was obvious the Big Bad was losing was the icing on the cake.
I'm sure I'll remember more later