Wind Release: Rasenshuriken

The Wind Release: Rasenshuriken was created by Naruto after he had mastered the Wind Release: Rasengan. By manipulating the wind chakra of the Wind Release: Rasengan, Naruto was able to create four large points making the Rasengan appear as a giant shuriken, with the Rasengan in the center remaining a perfect sphere. The technique gives off a loud bell-like screech.

Effects
When the Rasenshuriken hits a target, the victim becomes trapped in a giant vortex of microscopic wind-blades that attack the body on a cellular level. It produces so many individual strikes that even Kakashi Hatake is unable to count them all with his Sharingan eye. The wind chakra severs the chakra and nerve channels in the body, and if the chakra circulatory system is damaged, it can't be repaired by any form of medical ninjutsu (in a manner similar to poison as stated by Tsunade).

Other than the damage done to his cells, Kakuzu's body was left intact after being struck with the initial version of the Rasenshuriken. After Naruto perfects the technique through use of senjutsu, the damage is greatly increased; not only is it capable of cutting through rock, but when the Human path is struck by it, its body is ripped to shreds.

Improvement
When Naruto first begins using the Rasenshuriken, it lacks stability and is prone to dissipating before it even reaches its target. For this reason Naruto must use it as a melee weapon and force it into the opponent, similar to the Great Ball Rasengan. That's why, to succesfully use the Rasenshuriken, Naruto first needed shadow clones to distract the opponent, so that he could sneak up from behind. However, the greatest disadvantage of the melee use of the Rasenshuriken is that it causes the damage done to the opponent to also be done to Naruto, breaking his arm and doing limited cellular damage to it after using it against Kakuzu. Through repeated use this would leave Naruto unable to use jutsu again, prompting Tsunade to label it as a kinjutsu.

When Naruto learns senjutsu, he encases the Rasenshuriken in chakra to maintain its shape. This allows him to throw it at opponents, removing the possibility of it damaging himself. He is also able to expand it after it has been thrown, compensating for imprecise aim or fleeing opponents by widening the area of effect.

Under his own power, Naruto is left very fatigued after use of the Rasenshuriken due to it needing great deals of chakra to be performed. While in Sage Mode he can use it twice in addition to a Rasenrengan, and can then enter Sage Mode again to restore his number of uses.

Trivia

 * In the second Naruto artbook, when Naruto is in his initial jinchūriki form, the Rasenshuriken is colored red. Masashi Kishimoto notes this to be because, like the Rasengan, he has yet to decide upon a color for the jutsu.