Currently on Cartoon Network - Death Note
This genius kid
finds this Death God's book
if he writes down a person's name in the book and knows what they look like they will die in 26 seconds of a heart attack. The kid decides he's going to make the world a better place by killing off all the criminals.
Have fun - I've never blown through so many volumes of a manga so quickly to get to the end. The Anime is better because the diatribes that are in the manga are cut down for the sake of story pacing.