Came across this image so I decided to post it as a follow on to the previous article discussing Shuriken.
A cross-shaped shuriken, as described in the previous article and used in the movie is a Juji Shuriken, so named because a cross resembles the Japanese character for the number ten. So some four-point shuriken are in effect called "Figure Ten Shuriken".
Three-point Shuriken are called Sankou, which means "Three Rays". They may also be called Mitsubishi which means "three diamonds". Now you know why the car company uses the logo that it does.
The square shuriken with concave edges seems to appear in movies a lot. This type are called Senban Shuriken. Many modern shuriken on sale are of this type since they are probably very simple to manufacture. Concavity and therefore acuteness of the points will vary and they may or may not have sharpened or beveled cutting edges. A similar design to these are the Taisha Ryu Shiken Shuriken. These look very similar but have thickened tips and sharpened edges and are apparently made from quite thick and heavy plate so inflict considerable cutting and penetrating damage.