How do you kill a ninja? I've see the "ask a ninja" thing, but I think there's gotta be a simpler way...?

I know psychokinesis is a good bet (Psychokinesis: the ability to telepathically make things happen using nothing but thoughts) and guns are not, for they can dodge a bullet as easily as you or I might punch George Bush. And nuclear warfare just backfires. Magic seems to bounce off them, and mutants will get slaughtered. And no, I'm not on drugs. I'm a mad scientist.