18+ Tenjou Tenge

In one unusual Tokyo high school, education takes a backseat to brawling as warring clubs wreak havoc in the hallways and chaos in the classrooms, all vying to be the baddest team around! Although they often contribute their fair share, only a handful of students serve to stem the tide of violence in this untamed outpost. These are the few, the proud, the powerful: the members of the Juken Club!

(Source: CMX)