Tenjho Tenge, anyone? Another very good work by Oh! Great.
The story follows Nagi and Bob, two delinquents who have only one thing on their mind: becoming the strongest fighters around. When they transfer to a new school and attempt to take it by force, they meet several members of a martial arts club that show them their place. (Practically) Forced to join the club, they now begin training to become even stronger as they become entwined in something much bigger than themselves.
Some very unique artwork in this one as well as some very memorable characters. The summary may not say much, but I haven't read it in a while. If you're into Seinen manga, you should check this out.