Flying Thunder God Kunai

The are  and signature tool of Minato Namikaze, who uses it in conjunction with his Space–Time Ninjutsu: the Flying Thunder God Technique. They differ from a standard kunai in that they have three blades instead of one and on the handle (which is thicker than normal) is the "marker" for Minato's teleportation ability; Minato also said that these blades are bit heavier than a normal kunai. The prongs on them also makes it more deadly in melee fighting.

Minato gave one of these kunai to his pupil Kakashi Hatake, as a celebratory gift for his promotion to jōnin as well as to be able to teleport to his team at any time as long as they had the kunai in their possession. During the Third Shinobi World War, in the battle between Konohagakure and Iwagakure, the ninja from the former threw these kunai behind enemy lines which allowed Minato to instantly teleport to the various locations and slay the opposing shinobi, while at the same time making it difficult for the enemy to predict where he would teleport to next. He also kept several of these blades at his safe houses, so he could teleport there quickly when necessary.

Utilised Techniques

 * Flying Thunder God Technique
 * Flying Thunder God: Guiding Thunder
 * Flying Thunder God — Second Step
 * Spiralling Flash Super Round Dance Howl Style Three

In Other Media
In Naruto Shippūden the Movie: The Lost Tower, Minato placed one of these kunai over the source of the Ryūmyaku to seal it. Mukade managed to remove the kunai by absorbing the seal, which also triggered a huge lash of energy that propelled him backwards in time by 20 years, and Naruto Uzumaki and Yamato by 14 years.

Trivia

 * Although unnamed in the manga, they were named by Minato in Naruto Shippūden the Movie: The Lost Tower.
 * Tobirama Senju, the creator of the Flying Thunder God Technique, used regular kunai in a similar fashion by marking them with his own formula for the technique.