Gunbuster: トップをねらえ！ (Gunbuster: Aim for the Top!)

Alternate name: "Gunbuster : Top wo nerae!" In this game, you play female giant robot pilots defending the human race from aliens. However, the girls are still high-school-age students, and spend as much time teasing and tormenting each other as they do fighting. You can put a tack on the cockpit seat of another girl, write graffiti all over someone else's robot, and spread rumors of them being lesbian, among other things.You encourage your own character, and yes, you do fight the aliens. Art is by Mika Akitaka, who is the artist behind "Galaxy Fraulien Yuna" and is the mech designer of "Martian Successor Nadesico"