Shapeshifting. It's just totally freaking awesome. "Oh hey, I can make myself fly, or be super strong, or be super fast, or have breasts, or make my hands into axes."
Since they both have superpowers, I think the following hero and villain count.
Josuke Higashikata for heroes and Dio Brando for villains. Josuke's very much a normal kid, he just happens to also be a badass with the power to "repair objects". This has been used to heal the injured, steal wallets, cheat at the lottery, and make homing bullets out of glass. Of course, his Stand is also a close-combat type, so he can beat the shit out of people WITH HIS BRAIN.
Dio Brando has all sorts of crazy vampire powers (Regeneration, creating spawn, freezing blood, eyebeams...) and is probably one of the most straight-up evil fictional characters ever. Yet his is an elegant, refined evil-he is incredibly cool and incredibly repulsive at once.
Oh, and then he gains the power to stop time and beat people up with his brain. Lots of knife-throwing ensues.
Plus, he really knows how to make an entrance:
Yeah, he wears hearts. If you want to complain, say it to his face.