The correct name for this multi-bladed weapon is Shuriken and often called a 'throwing star', with between three and eight points; four being common. (See also Star Cross.) There are several styles: smooth blades, arrow heads, barbs, etc. (See also Barby Cross.)
They were never tools of first choice for ninjas, but the name has been borrowed for this implement to make it sound more exotic.
Easy to throw, but a bit awkward to catch. They are banned in many countries and a nightmare for veterinary surgeons who treat dogs trained to catch Frisbees.
And that's all we have to say about these implements. As for the Ninja, well, they are famous for sneaking around at night, always alert and ready to change tactic1. Their stealth can best be summed up in this little story.