I'm going to nominate the Sugar-Man as one of the weirdest supervillains out there.
Scarface and the Ventriloquist are bizarre, and their profile is only going to go up due to that Chris Nolan-verse fanfilm they were in. (Link: http://www.youtube.com/watch?v=9_ioQP1XU3s)
Hulk has his share of bizarre villains, as well as the Flash. Spider Man, Batman, Superman, practically everyone has had their share of weird C list villains. For Spider man, it's gotta be the Spot.
I'm probably missing tons, which is why I wanted to get your opinions. Who is the weirdest villain used in comics?