 If you liked
Gantz
|
 ...then you might like
Mahou Shoujo Site
|
Mahou Shoujo Site is basically a magical girl remake of Gantz (which is basically a seinen action remake of the mahou shoujo genre ;) ). People get chosen by a supernatural force, they kill each other and stuff happens. What makes Mahou Shoujo Site stand out is the great characters and a solid story (and lots of violence!). In my opinion it has more in common with Gantz than Madoka Magica.
Individuals are chosen by a supernatural force which results in a lot of death and carnage. Both series are filled to the brim with brutal, unflinching violence, and similar action where anybody can die at any time. Both series also have a nihilistic tone so if you liked Gantz you might like Mahou Shoujo Site.