 If you liked
Gantz
|
 ...then you might like
Mahou Shoujo Madoka★Magica
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Gantz and Mahou Shoujo Madoka★Magica are very similar in the story line.
Gantz is way more violent and has some sex, but basically, in both anime they have to go to a different dimension(basically) and kill something because they are being told to. In both animes they have to survive, some might make it, some don't, and the ending has a twist.