A shuriken (手裏剣) is a star-shaped throwing , mostly for Assassins,Shinobi and Kunoichi, a deadly weapon to use. It takes a great deal of practice to properly aim and throw this projectile.It is possible to recover the shuriken that has been thrown but miss the target (ie hitting the wall and dropped into reachable surface).
There also exists a variant of the shuriken known as the super-shuriken.