I've never really had a weird plot that I never ran with. I mean yes, in the past I've had ideas that I felt were too strange for the people or forum I made my home, but those ideas often got refined into something that people later enjoyed. 

One example was an RP that involved little angel girls going on a quest together. It had a simple yet interesting magic system that is most similar to avatar: the last air-bender. Each angel had one of the four elements and could use them a certain way. The players were going to go through a lot of fairy tale like landscapes on their way to the "empire of dirt" where they would do battle with whatever was draining the world dry. It was a private forum, and the players were all adverse to playing females and were hyper masculine. The final version still had angels in it, but it was more symbolic. The angels looked like humans, were older, and could be men. Even in the original version there were male angels, but they didn't adventure much because of how their magic functioned. Instead of fairy woods, we had kind of an ancient world vibe.

The very strangest one I had was an RP about going through someone's mind. Just weird thoughts all of the players had, their fears, parts of their past, would manifest as characters. There were no sex deviant minions, but there's something surreal about taking your brother's entirely fabricated impersonation of his favorite non-speaking character in phantasy star online and making it fight his character. And that was just the tenth post. Somehow, that one actually completed.