I've only seen the first Naruto show, so I'm not that familiar with them, but I was thinking of playing a kind of super villain who uses Shadow possession, Shadow clones, maybe the rasengan or chidori, and his byakugan to basically be an assassin and exploit non-shinobi.  He could also walk on walls and water, of course, as well as disguise himself as others, maybe even using other illusions, but his primary method of attack against shinobi would be disrupting their chakra with martial arts or making them kill themselves.

I assume he'd have to at least be a chunin for those moves, though.