Kamatari

is a summon of Temari.

Appearance
Kamatari is a giant weasel with an eye-patch covering its left eye. It holds a large sickle that is almost as long as itself.

Abilities
It is summoned using Temari's Giant Folding Fan as a medium through the Summoning: Quick Beheading Dance, after which it slices down all in its path with enough force to decimate an entire forest. After it starts moving, it can't be seen by the unaided human eye.

Sasuke Retrival Arc
Temari wanting to finish off her battle with Tayuya, a genjutsu specialist, Kamatari was summoned through the Summoning: Quick Beheading Dance. In a split second, Tayuya is quickly finished off, much to Shikamaru Nara's surprise.

Ultimate Weapon Arc
Kamatari once again makes an appearance in the last filler arc, where it is used as the main key to Shikamaru's strategy in an effort to bring Kujaku down.

Trivia

 * Kamatari is an obvious reference to the Japanese yōkai ; however, instead of being simply a weasel with razor sharp-claws, it is literally a with a.