A kunai is a Japanese tool possibly derived from the masonry trowel. Two variations are the short kunai and the big kunai. It is a good example of a very basic tool which, in the hands of a martial arts expert, could be used as a multi-functional weapon. It is commonly associated with the ninja, who used it to gouge holes in walls.
Kunai normally had a leaf-shaped blade and a handle with a ring on the pommel for attaching a rope. This would allow the kunai's handle to be wrapped to act as a grip, or when used as a weapon; to be strapped to a stick as an expedient spear, to be tied to the body for concealment, or to use as an anchor or piton. Contrary to popular belief, they were not designed to be used primarily as throwing weapons, though they can be thrown and cause damage. Instead, they are a thrusting and stabbing implement.
In the popular culture mythology of ninja, the kunai is commonly portrayed to be a Japanese knife that is used for throwing as well as stabbing. The kunai is often portrayed in manga/anime and video games as a common weapon for ninjas (either primary or backup). The Kunai is also used as a weapon by Scorpion from the Mortal Kombat Series. Scorpion spears his opponent with the Kunai, which comes out of his hand. He uses the famous catch phrase "Get over here!" or "Come here!" when he uses his Kunai spear. Ibuki from Street Fighter is another example of using Kunai in fighting games. Ninja in the popular Japanese manga and anime Naruto all use kunais. Characters occasionally attach Paper Bombs to them, to create explosions.