Shuriken (Throwing stars) are weapons carried by the turtles. They are somewhat more refined than The Foot Clan's version. These throwing stars are one of Master Splinter's strongest weapons. They are also useful when striking The Kraang Droids.
Throwing stars, or Shuriken as they are traditionally called, are one of the oldest weapons in the ninja arsenal and have been made from a variety of materials including sticks, coins, washers, bits of glass, and nails. Basically anything that the ninja could lay hands on at the time.

Official Description

More refined than the Foot Clan version, Splinter's stars are silent and strong. - Nick