As requested by SK.
Gantz (ガンツ, Gantsu?) is a Japanese manga and anime series written and illustrated by Hiroya Oku. Gantz tells the story of a teenager named Kei Kurono who dies in a train accident and becomes part of a semi-posthumous "game" in which he and several other recently deceased people are forced to hunt down and kill aliens. The missions they embark upon are often dangerous. Many die on each mission, but others replace them in the same manner as Kei Kurono's appearance.
The Gantz anime, directed by Ichiro Itano and animated by GONZO, ran for 13 episodes and had a direct sequel called Gantz: Second Stage, which continued the series for another 13 episodes. Both seasons make up the 26 episode series. It was licensed in North America by ADV Films. The anime series is distributed in the United Kingdom by MVM Films, and in Australia and New Zealand by Madman Entertainment. At Anime Expo 2007, Dark Horse Comics announced it would release the manga in English.
(I personally havn't seen this yet, but once I get around to it, I'll state my opinion on it.)
