Gantz tells the story of Kei Kurono and his friend Masaru Kato who die in a train accident and become part of a semi-posthumous "game" in which they and several other recently deceased people are forced to hunt down and kill aliens armed with a handful of futuristic items of equipment and weaponry.
Theres not many animes with such dark, well written story and dialogue. and if your afraid it being to mature there more nudity in Queens Blade except for one episode. (havent seen the movie yet tho) I would say it reminds you alittle of Berserk and as special as Beserk a classic