S-rank

An S-Class shinobi is a ninja who has gained power and knowledge far beyond an average Jonin and have earned a legendary, or feared status. The title itself isn't an official rank and the village officially refers to them as Jonin, and is more of a casually-applied term instead of a formal title. Some ninja who have achieved this rank sometimes leave their villages to seek their own ambitions, such as most of the members of the Akatsuki, thus becoming missing-nin and having no rank at all. All of the major ninja villages put their S-Class missing-nin in the Bingo Book, marking them for assassination for all Jonin and ANBU ninja. Most ninja however adopt a "flee on sight" policy rather than to fight one. Most Kage's tend to be S-Class, and sometimes a team of S-Class ninja would be given nicknames by their allies and enemies, such as the Sannin.

Konoha

 * Naruto Uzumaki: "The #1 at Surprising People"
 * Kakashi Hatake: "The Copy Cat Ninja"
 * Tsunade: "The Legendary Sucker"
 * Might Guy: "The Green Beast"
 * Jiraiya: "The Toad Sage" (Deseased)
 * Minato Namikaze: "The Yellow Flash" (Deseased)
 * Kushina Uzumaki (Presumed Deseased)
 * Sakumo Hatake: "The White Fang" (Deseased)
 * Hiruzen Sarutobi: "The Professor" (Deseased)

Akatsuki

 * Pain: "The God of the Rain"
 * Konan: "Pain's Angel"
 * Itachi Uchiha: "Itachi of the Uchiha"
 * Kisame Hoshigaki: "Monster of the Mist"
 * Deidara
 * Hidan
 * Kakuzu
 * Zetsu
 * Sasori: "Sasori of the Red Sands"
 * Madara Uchiha

Team Hawk

 * Sasuke Uchiha: "Sasuke of the Uchiha"
 * Jugo: "Jugo of the Scales"
 * Suigetsu Hozuki: "Demon of the Mist"

Otogakure

 * Orochimaru: "The Giant Snake"
 * Kabuto (Possibly)

Sunagakure

 * Gaara: "Gaara of the Sand"
 * Chiyo

Kirigakure

 * Zabuza: "Demon of the Mist"
 * Raiga: "Thunder of the Mist"

Kumogakure

 * Kirabi: The Killer Bee