I just don't want to lose this in the ether:
Throwing Master 
I'm curious if it would be effective in DF. Possibly, depending on the way you put the character together and just how many effective throwables you could carry. Cornucopia Shuriken would be interesting - I'd be tempted to make it a bandoleer, which always shows three of them but never seems to run out. That fits basically every comic book ninja ever!
By the way, GURPS Martial Arts has two different rules on throwing lots of stuff.
One is based on Rapid Fire. This was heavily inspired by Ogun, the ninja master in Kitty Pryde vs. Wolverine - especially the amazing panel where he bursts into the scene in a seeming cloud of shuriken. This is the "hurl a big handful of things, and see who gets hit" approach. It's very useful when using very small, very low damage weapons, where quantity is the quality.
The other is based, more realistically, on actual shurikenjutsu techniques. The sources I read on shurikenjutsu emphasized rapid throwing - one after another, with a quickened rhythm as you went. So each successive shuriken would come with just a slightly lower delay between throws than the last one. This was designed to catch people off-guard. One source - a (former) samurai in the Meiji era - mentioned using shuriken in this way, aiming to catch a troublemaker recidivist samurai type off-guard with a shuriken toss. Dodge one, each the next one as you get into a rhythm and the thrower does not, and now you're trying to swordfight with a shuriken sticking out of your leg. Concealing shuriken and throwing them as part of a standing katana drawing motion was another - a Deceptive Attack for sure. Fun stuff - and a good tonic to the "ninja use shuriken, samurai don't" meme that doesn't reflect any actual sources that I could find.