Shouwakusei wo Butsuketekuru Lolicon Kara Chikyuu wo Mamoru Geimu
Caveats: Lolicon (obviously)
And you thought the Evangelion mahjongg game had a long title; this one comes close to matching it. This is an amusing concept and one of my favorite games of this genre. The idea here is, you in your space battleship full of an infinite supply of robots must defend the earth from descending meteors and enemy robots commanded by lolis. Power-ups include multiple shots and larger robots to launch, though you need to collect five of each in order for them to take effect. You can also collect hearts that heal the planet (there's a hippie joke here somewhere), as well as life powerups to repair your ship. As you destroy bosses, the girl you chose strips. The artwork is spectacular and this game is both challenging and addictive.