Kisame Hoshigaki, known as Monster of the Hidden , was an S-rank missing-nin from Kirigakure's Seven Ninja Swordsmen of the Mist and was partnered with Itachi Uchiha when the latter joined Akatsuki.
Kisame was one of Itachi's "few friends." While Kisame was often proud and brutal, he would refrain from attacking or killing if not commanded by Itachi. His respect of Itachi was so strong that while admitting he would not be enough to take on Jiraiya, Itachi could possibly stand a chance against the legendary Sannin.
Kisame first appeared when he and Itachi infiltrate Konoha. It is at this time that he first meets Guy and seemingly just have fun with some of Konoha's top jonin. We them see them at the hotel where they attacked Naruto. While they came close to capturing Naruto, Sasuke interrupted them and distracted them from their goal long enough for Jiraiya to come and save Naruto.
The next time we really see Kisame is when he decides to take on Guy's Team. While he wants to fight Guy again, it is decided that he use a close to fight off the team. He is quickly able to trap Guy's team in water prisons, and takes Guy on himself. While he fights Guy, he realizes that the clone has strong limitations as it only has about 30% of Kisame's real chakra. Guy, however, is forced to open the 6th Gate of his Chakra Pathway System to defeat the clone.
Kisame is later seen lamenting the death of his "friend" Itachi. He knew his partner chose his death so he already knew before Sasuke went in that it would be the last time he would meet Itachi. After this, Kisame meets his untimely death when he tries to capture Killer B, the 8 tails' jinchuriki. He attacks B but is quickly betrayed by his own sword, Samehada (who switches loyalty to those with high level of chakra). Bc he is betrayed by his own sword, which lends chakra to B, he found himself surrounded by B and his brother, the Fourth Raikage. Upon being decapitated, it is revealed that it was actually a clone, and that he is hiding within Samehada.
Upon infiltrating enemy territory, Kisame is discovered by Naruto who is able to sense the hatred within his heart. Kisame escapes with Samehada, although Samehada again abandons him to return to B. While escaping Kisame runs into Might Guy, who again does not remember him. Instead Guy thinks Kisame is his "evil self." (what a moron haha). In an intense fight, Kisame forces Guy to open his 7th Gate. Defeated and about to have his mind probed for information, Kisame decides to sacrifice himself by having his sharks eat him alive! (that's commitment my friends)
Kisame was, in my opinion, another misguided soul that devoted himself to the wrong cause. He died valiantly to defend it, but still was nothing more than someone who had been manipulated for someone else's purposes. His last scene actually made me feel sad for him. Did anyone else sympathize?