Who is your favorite One Piece villain?
Mine is Blackbeard... For a number of different reasons. For one, he's one of the few pirates that looks and acts like an actual pirate. For another, his happy-go-lucky personality undermine his cruel actions, or at the very least, it creates an interesting and disturbing contrast. The fact that he's like a dark version of Luffy is another interesting factor, and it seems obvious at this point that somewhere down the (Grand) line, the Straw Hat Pirates will face off against the Blackbeard Pirates. And I look forward to it.
He's also very strong, even without his Devil Fruit powers (all two of them). Strong enough to scar Shanks back when he still had two arms. I could go into lots of different details about why I love this guy, but I don't feel like getting into it all right now.
Runners up include Gecko Moria and Crocodile. They're both evil parallels of what Luffy might have become. I'll admit that I find Gecko Moria more fascinating than Crocodile, because I would have liked to see what he was like before Kaido killed his crew, but Crocodile is pretty damn badass all on his own.