Ninja were people of feudal japan trained in Ninpo or Ninjutsu. It was possible to use skills learned in assasination-which was done, but not coldly. Ninja's were japans peace keepers and information gathers-they would assasinate political powers that threatned peace of japan, and would often be recruited by a higher power (such as a warlord like Oda Nobunaga, or Ieyasu Tokugawa) to spy on enemy's and gather information. Ninja were originally called *Shinobi*, literally translating into a expert at information gathering. Ninja groups were divided into families and clans. The two regions were Ninjutsu developed and Ninja were founded were Iga and Koga provinces. there were roughly 53 subgroups of Koga and Iga. One of the most famous Ninja in history was Hattori Hanzo-a famous warlord and Ninja of Iga.
Random facts:
In 1676, the book Bansenshukai about Ninja methods was written by Fujibayashi Yasutake, a Samurai of Iga castle.
In 1681 the book Shoninki (correct Ninjutsu memories) was written by Fujibayashi Masatake.
In 1653 the book Ninpiden meaning secret teachings of Ninjutsu was written by Hattori Hanzo Yasunaga.
There were very few ninja-when oda nobunaga attacked Iga, 80 ninja fled.
Genbukan and Bujinkan are the only organizations keeping true Ninjutsu alive today.
Ninja didnt wear black very often-they wore deep red or dark green when on missions, and in winter snow, White.
Ninja were often Samurai too-afterall its only Title, not material.
Ninja didnt...

a deamon ninja is someone who is a master of stealth and melee on halo, especilly with melee specified weapons such as the sword.

Coolass fighter
who were tight suits
to show off their kickass bodies!
hiiiiyaaaa!

A small Gnome-like creature from the Ratchet & Clank video game series. Highly annoying and carries twin swords that it tries to cut your crotch with.

A person, usually high school to college aged young white or Asian male, who purchases weapons, such as samurai swords, maces, spears, scimitars, fancy looking knives, daggers, and nun-chucks at a shopping mall, usually from stores like Merlot's Cutlery, China Capital Arts, or various privately owned Oriental gift shops. Will talk trash to each other about the quality of their swords, which they will never use for anything in real life. Some of these people will pay high prices to purchase "better" swords on the internet, in the range of $300 to several thousand dollars, to out-do their friends or enemies who bought their blades at the local shopping mall. These people are often goths, thugs, or kids who are at the bottom of the social totem poll.

Ancient Japanese warrior, well trained in the art of stealth. Some tools of the trade include shuriken, swords, daggers, and knives. Ninja were part of a clan.

Someone who is quick and proficient in their use of the english language for killing Samurai. They also carry swords.