Naruto: Way of the Shinobi

Academy Student
The academy is where would-be ninja start; they are not actually considered ninja until they graduate. Academy students take formal and practical tests of all sorts and are taught basic ninja skills, such as martial arts, techniques, physical fitness and the way of the ninja. Basic weapon usage, such as kunai and shuriken, is commonly taught. Elementary ninja techniques, though they vary from village to village, are also taught. Upon graduating, students receive a special band of fabric with a metal bar bearing the symbol of their village, which is commonly referred to as a "forehead protector" or hitai-ate, although it can be worn in different ways. Some villages also have an additional test given by the Jounin sensei of each three-man squad to see if they are truly ready to graduate, such as Kakashi Hatake's bell test, which determines whether the squad can work as a team. 


Genin
Genin are the lowest level of ninja and also the ones that display the most difference in power. When they become Genin, ninja start to do their bit for their village's economy – being sent on missions that the village gets paid for. They are typically sent either on D-rank missions, which are the lowest rank and are almost entirely risk-free jobs of manual labor, or experienced Genin are sent on C-rank missions, which are a cut above that and begin to verge on real "ninja" work – though they generally have a very low possibility of risk to the ninja involved, especially since their Jounin level sensei often accompanies them. 
Genin are put in four-man cells, consisting of three Genin and a Jounin sensei, in order to learn teamwork and experience true ninja life under the supervision and protection of an elite shinobi. The make-up of these teams is based on the individual skills of the Genin, so that there will remain a balance between the teams. The teams are usually made up of two boys and one girl, though there are exceptions. It appears that, usually, the four-man cells specialize in certain skills. Complementary skills also seem to influence team selection.


Chuunin
Chuunin are ninja who are qualified to watch over and guide other ninja. Chuunin have reached a level of maturity that primarily consists of leadership skills and tactical prowess. Some of them, function as teachers and others serve as team leaders in charge of small teams who need to make decisions and utilize the skills of the shinobi under their command to the maximum effect. Chuunin are typically sent on C or B-rank missions.
To become a Chuunin, a Genin participates in a large examination, known as the "Chuunin Exams," with his or her team. Theexam is a three-stage exam: the first stage tests their information gathering abilities and decision-making abilities (as well as their overall understanding of the ninja philosophy), the second stage tests their abilities at accomplishing a mission and adhering to guidelines, and the third consists of fights between those who passed the previous two stages, watched by a council that decides who becomes a Chuunin and who does not. While the winners are able to proceed to fight the next opponent, aptitude, rather than winning, is evaluated to determine whether a candidate is promoted. This way, anybody who makes it to the third stage of the Exams has a chance to become Chuunin. However, it is also possible for none of the candidates to become Chuunin if the judges believe that they do not have appropriate qualifications. Preliminaries may also be held if too many ninja teams reach the end. In the past, each village held their own Chuunin exam. After the 3rd Ninja World War, allied ninja villages agreed to hold the exams together at the selected village that would host the exam. This was done to improve relations between the villages and prevent war between them. Another advantage is that ninja that took the exam might attract clients who are interested in hiring them. Because of the growing number of ninja in each village, the exams are hosted twice every year. Upon reaching Chuunin level, ninja can wear an identifying tactical vest that holds ninjutsu scrolls. This vest is not required; instead, some look for more elaborate clothing like capes or robes.


Jounin
Jounin are generally highly-experienced ninja with great individual skill who serve as military captains. They are often sent on A-rank missions, and experienced Jounin may even be sent on S-rank missions (which are considered to be the most difficult). They may also carry out these missions alone. They are sometimes assigned as sensei for three-person teams of Genin. Most Jounin are able to use at least two types of elemental jutsu (chakra nature).


Special Jounin
Special Jounin are ninja who, rather than all-around Jounin training, have Jounin-level ability in a single area or skill, much like warrant officers of real-world militaries. They are elite specialists in their areas and are often assigned as subordinates to regular Jounin when their services are needed.


Kage
Those who have achieved the title of Kage are the leaders of the five most powerful Hidden Villages and generally the most powerful ninja in their respective villages. There may be exceptions, however; for example, a ninja may be the most powerful at the time of being installed as Kage, but may become less powerful upon aging, eventually being surpassed by a more youthful ninja. A Kage may retire and give the title to someone else; the title, once granted, is held permanently. This creates a case where there are two Kage at the same time, with only one of them actually active -- as was with the Fourth Hokage and the Third Hokage, where the latter had given up the title to the former, only to come out of retirement when the former died. Their elite status is also attributed to the tendency for most Kage to have family members who were previous Kage, or be personally taught by a former Kage or student of a former Kage. 
The five Kage have different titles depending on their village. Those titles are:
Hokage - Kage of Konohagakure.
Kazekage - Kage of Sunagakure.
Mizukage - Kage of Kirigakure.
Raikage - Kage of Kumogakure.
Tsuchikage - Kage of Iwagakure.
The Kage stand equally with the rulers of their countries, oversee the activities of their villages, and are the leaders of ninja society.


ANBU
The ANBU protect the village from exceptional threats, conduct high-risk missions into enemy countries, and deal with extremely strong ninja. They are also responsible for carrying out assassinations and missions requiring specially trained ninja. All ANBU carry Ninjatō, which are usually strapped to their backs, and they all know the layout of the human body in detail. By using Temporary Paralysis Technique, ANBU members can paralyze an opponent, leaving them open for attack. With Time Reversal Technique, an ANBU can put someone in a state of reverse hypnosis, allowing them to remember details that they otherwise would not.
ANBU is an organization that serves under the direct command of their Kage. Kakashi Hatake was a former captain and Itachi Uchiha became an ANBU captain at age 13. Ibiki Morino, the proctor of the first Chūnin exam, is the head of the Konoha ANBU Torture and Interrogation Squad. Zabuza Momochi and Raiga Kurosuki were once part of Kirigakure's ANBU.


S-Class
S-class ninja have gained power far beyond an average Jounin and earned a legendary status. This title is merely a class rather than an actual rank; the ninja's official rank with a village will usually still be Jounin. However, it can sometimes be lower, or they can have no rank at all. The allegiances of these ninja range from being part of the village's own ninja to being wandering ninja who are still loyal to their village. Some ninja of this level tend to leave their villages behind to seek their own ambitions, thus becoming missing-nin. The ninja organization Akatsuki is originally composed of ten S-class missing-nin. Ninja of this class are often noted in the Bingo book, a list of notable enemy ninja marked for assassination that each ninja village provides for its Jounin and ANBU squad members. Most ninja, even high-level ones, choose to flee rather than face someone of the S-class.
Ninja of the S-class are often highly revered, and usually signified by nicknames allies or enemies give them. One group of ninja who have gained this special status are the Sannin, or "Legendary Three Ninja" of Konoha: Jiraiya, Orochimaru, and Tsunade. Most Kage also tend to be in this class. For example, the third Hokage was called 'The Professor' due to his vast knowledge of ninja techniques.


Medical-nin
Medical-nin are ninja who specialize in medical treatment and use medical-oriented jutsu to heal others. Becoming a medic-nin requires a great level of intelligence and excellent chakra control, since medic-nin use chakra to heal injuries. Aside from their medical training, their combat training consists mainly of taijutsu skills, with emphasis placed on evading enemy attacks. This is because the death of the medic-nin could result in the death of the team. On dangerous missions, a medic-nin will usually be sent along with the team, to increase the survival rate of that team. The most basic of medical jutsu is the Mystical Palm Technique, a multipurpose technique that can heal wounds and perform surgery. To heal with the ability, users collect chakra to their hand to speed up cell regeneration wherever it is applied. For the latter, the user focuses their chakra into a blade to make cuts where necessary, though because the blade is made of chakra the flesh is never cut. This aspect of the ability can be used in combat, though it requires great precision to be effective. For more severe injuries, medical-nin perform the Healing Resuscitation Regeneration Technique, which utilizes a part of the user's body as a medium to heal their injuries. The technique requires a great deal of time and concentration, with medical personnel needing to switch places so that they can rest.


Hunter-nin
Hunter-nin are a special team within the ANBU, given the specific duty of hunting down missing-nin. They kill their target, taking the head as proof, and then completely dispose of the body by using various methods, such as cremation or the summoning of wild carrion crows to devour the corpse. This is done in order to make sure the village secrets which a ninja's body holds -- such as chakra types, herbs eaten, ninjutsu, special medicine, and kekkei genkai -- will not be revealed to outsiders. Hunter-nin are also supposed to destroy the corpse at the very spot the body is lying; it is not to be moved after it is dead. As a requirement, they must possess a thorough and intimate knowledge of human anatomy. Due to their reputation for utterly and completely obliterating the remains of their targets, they are code-named "The Undertaker Squad." 


Missing-nin
Missing-nin are ninja who have abandoned their Hidden Village, and as such can include ninja of every rank. These ninja are considered traitors and are hunted down because of the secrets they may hold. Other Hidden Villages would be interested in purchasing this information because it could be useful in gaining an upper hand in battle or obtaining a bloodline limit unique to a village. Villages create special units of hunter-nin to take care of this problem, although it's unlikely that every missing-nin has a team of hunter-nin sent after them. 


Courier-nin
Courier-nin are ninja that deliver packages from one point to another. They take on extremely dangerous delivery jobs that others will not; these jobs can even be life threatening in nature. They use smoke to communicate with each other over long distances, and are a very determined group of ninja, taking the "postal motto" to new heights. They never deviate from their goals, and perfectly adhere to rules, regardless of what will happen if their package is delivered. When asked their name, they will use their designation number. 


Cooking-nin
Cooking-nins are ninja who were originally intended to cook for other ninja in their squad. The theory was that ninja who ate good food would also perform well. This idea backfired as ninja ate too much of the food with "too much flavor", making them too fat to be able to complete their missions effectively (The confusion comes from the fact that it is called an "aku" recipe. The cooking-nins were under the impression this stood for akuma, or demon. It actually stood for akunuki, meaning removing bitterness).


Seven Ninja Swordsmen of the Mist
The Seven Ninja Swordsmen of the Mist is an organization consisting of only the greatest blade wielding shinobi of their generation that Kirigakure (Mist Village) can produce. There can only be seven members at a time — hence the name. The swords of the Seven Swordsmen are passed down from generation to generation.

Kubikiribōchō A giant sword with a butcher-knife-like appearance, the wielder can use the semi-circle on the blade to decapitate an opponent's head, hence the name. The sword has an ability to regenerate using the iron absorbed from the blood of those it cuts down. It is also called a "Seversword".

Samehada (鮫肌; Literally meaning "Shark Skin"): The most terrifying of the seven blades, it has the appearance of a giant knife covered in shark scales. It is a sentient, living weapon and has the ability to "eat" chakra. It is also called a "Greatsword" (大刀, Daitō).

Nuibari A sword in the shape of a needle with a long thin wire that resembles thread attached to it, which can be used to pierce enemies and "sew" them together in human bundles. It is also called a "Longsword".

Kabutowari  A sword consisting of a single sided axe and a hammer joined by a length of chain. Said to be capable of crushing any and all defences. It is also called a "Bluntsword".

Shibuki A sword that has a scroll full of explosive tags incorporated into it, lined up behind the blade, combining swordsmanship and explosions. It is also called a "Blastsword".

KibaTwin swords that are imbued with lightning which increases their cutting power. They are said to be the sharpest swords ever forged. They are also called "Thunderswords".

Hiramekarei A bandaged double-handled sword that is capable of storing and emitting the user's chakra which can then take on various forms. It is also called a "Twinsword".