Shuriken

From Narutopedia

A shuriken (手裏剣), like kunai, is one of the more basic weapons seen in Naruto. They are sharpened, four-pronged metal stars, useful for throwing. Although small, they can be used to distract, or, if accurate enough, can be deadly. They have an open circle in the center, used for grabbing with a finger, to avoid cutting oneself, or to put thread through. The circle is also a benefit in aerodynamics, as it ensures more accurate trajectories.

In addition to the basic shuriken, larger, arm-length shuriken have been seen in the series. They are usually carried on the back. The Fūma Shuriken is of a similar size, but is more lethal and can be folded together for easier storage.