Iron Man hands down. Not because I feel any particular connection with Tony Stark, but the man has an armor for every occasion. And come on, who wouldn't want a tricked out robotic suit like that? As for villian?
I am disgusted that I'm the first person to pick Joker. Any villain can have a master plan, but to have a master plan and be a completely off your rocker? That's talent. It doesn't matter what hair-brained scheme it is, it always have some underlying goal. And you get to fuck with people. Make a bomb threat! Make the "bombs" nothing more than marzipan and kittens. The best part? He doesn't need any powers. No freeze rays, no control over plants, no mutations, no devices pumping him full of venom. His brain is his weapon alongside batshit insane logic and a moral system so loose there's no word to describe it. And that's what makes him so damn scary.
If I were a villain... Heck, I already am one! :P
But really, Catwoman. A hero and a villain. Super talented, and pretty darn smart. Plus, she doesn't need super-powers to kick but. :)