AoS Hira shuriken

Age of Sword

Hira shuriken (平手裏剣) - small star-shaped blade, that was generally used for throwing, usually it is associated with shinobi, however, were often used by samurai as well (for example, one of the oldest bujutsu schools, Tenshin Shōden Katori Shintō-ryū, includes shurikenjutsu.

Contrary to popular belief, shuriken were not primarily intended as killing weapons, but rather in a secondary role as a nuisance or distraction. Targets were primarily the more exposed parts of the body: the eyes, face, hands, or feet. Actually, there are only one or two small spots on human body, were shuriken hit may be sometimes lethal - mostly on the neck. And no, shuriken can't penetrate skull.