GURPS Martial Arts is a book with lots of different martial arts styles for your characters. It also includes maneuvers, which are like skill subsets. I really like how this book lets you build your own martial arts styles. Martial Arts also includes tables for all the weaponry, such as Sai (for anyone who's ever watched Teenage Mutant Ninja Turtles, Raf uses a pair of these).
A lot of the illustrations are gory, reminding you that GURPS was never meant for kids (Steve Jackson Games should make that clearer, I think). BUT, aside from the "Silly Combat Rule" Bulletproof Nudety, there's no adult content! And while there's gore in some of the pictures, everyone's fully clothed. That's really, really nice.