Despite the Ninja craze of the 1980s, the historical Ninja shuriken (or stars) were only used as distraction weapons with an effective range of a mere 16 ft and even then with a direct hit caused superficial wounds. Being crude metal weapons with a simple hole in the middle and 4 blade points and often engraved (which caused aerodynamic instability)... they are very difficult to throw accuractely and against Samurai armor plating proved largely useless. Samurai armor was articulated and had throat protection too! The Ninja historically (even a female one- Kunoichi) had more success with powders and flash explosives or their main weapon the Ninja sword. But Hollywood and HK Cinema still perpetuate the myth that shuriken were successful offensive weapons when they were not. They were for defensive purposes at close range against unarmored targets and even volleys of them seldom caused death!!!