Quote from Pebble_
Hard to find : Real antiheroes, with no moral sense whatsoever, who do whatever the hell they want, and mostly terrible things. Like Revy in Black Lagoon
Even harder : Gambler or swindler protagonists or anything where the hero uses his brain to pull gambits on the people around him. Said gambits ...
agreed. Those aren't really antiheroes, but villians
Shamo, in my opinion, is the most true villian as a main character that I've ever seen
Spoiler (mouse over to view)
He rapes someone's girl just to piss him off. Real rape. My god o_o Never ever thought a manga would go so far. I'll finish shamo eventually... when I'm under a little less stress and am a little more mentally stable
Surprisingly enough though, it's hard to find good "hidden powers" mangas.
My all time favorite mangas: http://tinyurl.com/my-top-manga