shuriken
A shuriken, commonly known as "throwing stars", is a traditional Japanese concealed weapon that was generally for throwing, and sometimes stabbing or slashing.
They are sharpened hand-held blades made from a variety of everyday items such as needles, nails, and knives, as well as coins, washers, and other flat plates of metal. Though it is commonly depicted in popular culture as a multiple bladed (usually three or four) throwing weapon with a hole in the middle as a holding point.
This weapon is commonly used by ninjas.