The Kunai is harpoon-like weapon used by Scorpion from Mortal Kombat onwards. Chameleon also used these weapons in Mortal Kombat Trilogy, Reptile uses this weapon in Mortal Kombat and Smoke and Noob Saibot use this weapon in Mortal Kombat II. In Mortal Kombat Legacy it says that Scorpion was a master of the kunai.
There are two kinds of Kunai: Big Kunai and Short Kunai.
The ninja spectre Scorpion chose this particular blade as his own favorite weapon in both life, and death as he continued to use it in battle and even slaughtering his foes and anyone who dared to get in his way throughout the entire Mortal Kombat legacy, especially when he shouts his famous catchphrase "Get over here!" as he pierced his opponents with this attack.
The weapon had evolved over the years; first with the Kunai attached to a rope, then with the Kunai attached to a metal chain. However, in the Mortal Kombat (film) continuity, including Mortal Kombat: Conquest, Scorpion's "spear" is a sentient, serpent-like being that emerges from a hole in his palm and strikes at his command.