Samehada

is a large living sword comparable in size to the Kubikiribōchō. It is described as "the most terrifying of all the Seven Swordsmen's blades".

Background
After Kisame killed its former wielder, it came into his possession. The two had a long history together, leading Kisame to become regarded as a "tailed beast without a tail". They were together for so long in fact that their chakra signatures even became identical, which Kisame uses to his advantage on one occasion to hide within Samehada and avoid detection by sensors. During Kisame's fight with Killer B, Samehada grows fond of B's chakra and betrays Kisame, giving B back some of the chakra it had absorbed from him during their battle and even shielding B from Kisame's attacks. Despite this, Kisame is able to force Samehada to cooperate with him, allowing him to hide within it to infiltrate Kumogakure as a spy and forcefully use it to absorb B's chakra. After Kisame's death, Samehada actually cries for him giving even more lifelike characteristics to the blade. During B's fight with Itachi, it is revealed that Bee keeps his Super Vibrating Lightning Release Sword within the mouth of Samehada.

Appearance
At the tip of Samehada's handle is a small skull. Though mostly wrapped in bandages its actual blade is covered in scales. Samehada grows larger from the chakra it absorbs, its scales becoming longer resembling shark fins and its mouth, located at the tip of the blade, becoming more pronounced. Keeping Samehada wrapped in bandages apparently inhibits this growth

Personality
Samehada is unique for being a sentient weapon that gains nourishment from the chakra of others. The blade is happiest when engorged with chakra. As a sentient weapon, Samehada chooses its user. If someone it disapproves of tries to wield it, spikes protrude from the handle, forcing them to release it, and Samehada returns to its chosen owner.

Abilities
Its actual blade is covered in scales, which causes it to inflict shredding or shaving damage rather than cutting what it comes into contact with. The effect is similar to a shark's skin, hence its name. While it ordinarily remains rigid, Samehada is able to stretch and bend to a great extent, allowing it to be used like a flail.

Although it constantly feeds off of the chakra of its owner, its largest "meals" come from fights wherein it absorbs the chakra of its owner's opponents. Such an ability allows Samehada to literally slice through an opponent's technique and even prevent techniques from being performed by absorbing all of the opponent's chakra. This is particularly useful when fighting jinchūriki, as Samehada can quickly deplete their large chakra supplies as well as remove their chakra cloaks. However, it seems to be unable to automatically absorb ambient chakra, in all instances where it's absorbed chakra are when his opponent had a visible aura around them.

While the ability to absorb chakra is useful in defeating opponents, it is also beneficial to its user. Samehada has the ability to transfer the chakra it has absorbed to the wielder by partially fusing with its wielder, so it can be used to either heal the wielder's injuries or replenish their chakra reserves. This makes the wielder of this sword extremely difficult to defeat. It is drawn to others with large chakra supplies, allowing it to be used as a sort of sensor. A wielder of this sword, such as Kisame Hoshigaki can take this fusion one step further by completely merging with Samehada. Doing so causes him to become much more shark-like in appearance, growing fins and webbed hands that allow him to move through the water with greater ease. Kisame receives some of Samehada's abilities while in this form, such as being able to extend spikes form his body for attack, and absorbing chakra when others come into contact with him, as well as the ability to track chakra.

Trivia

 * Suigetsu Hōzuki wishes to gain Samehada for himself, something he planned to accomplish by killing Kisame.