Mavericks

The Mavericks are Reploids (robots with free-will) who rebel against the humans. Their main goal is to destroy the humans to create a perfect world only for Reploids.

Megaman X
The term Maverick is used to identify a Reploid that goes berserk and violent, be it by a programming error, viral infection or by his own will. A Reploid can also be wrongfully labeled mavericks due to mistakes. Sigma led the Mavericks rebellion against humanity. There isn't just one kind of Maverick, as their reason for becoming Mavericks can vary.
 * Error Mavericks: These Mavericks goes insane because of some kind of error on their programming. The best example is Vile.
 * Viral Mavericks: The most common kind of Maverick, they are infected by the Sigma Virus. The virus corrupt their programming, making them believe that humans are inferior and must be exterminated. Depending of the level of infection, a Maverick can become completely berserk, destroying everything in it's path.
 * Free willed Mavericks: These Mavericks choose to go against the humans by their own will. They become evil by their own selfish desires. They are more rational than the other Mavericks, which doesn't mean they are less dangerous.
 * Political Mavericks: These Mavericks aren't really Mavericks. They are labeled as being Mavericks for political reasons or misunderstandings. The best example is the entire Repliforce, who were wrongly accused of being Mavericks because of their presence at the moment that the floating city of Sky Lagoon was destroyed, and for refusing to drop their weapons. Other Political Mavericks include mercenary groups that hunt Mavericks illegally, such as the Red Alert Syndicate.

Megaman Zero
The term is now used to identify any Reploid who opposes the rule of Neo Arcadia. Copy X wrongfully accuses many Reploids of being Mavericks, retiring every one of them. The scientist Ciel then forms the resistance against Neo Arcadia. Later, when Dr. Weil take control of Neo Arcadia, he labels Maverick on anyone who opposes him, be it human or Reploid.

Megaman ZX
After countless wars, humans and Reploids call a truce between themselves. As the Legion and the Sage Trinity are formed, it is decided that every human will receive bionic parts and every Reploid will be given a life-span, so everyone should go to Legion to be inspected. Anyone who disagreed to these rules would be labeled Maverick and expelled from the Inners, the cities at that time who were protected by large domes. The Mavericks started to organize themselves and make large-scale attacks to the Inners. Later is discovered that they were under the influence of Model W, who can corrupt machines just like the Sigma Virus.

Trivia
The Sigma letter is seen in the Maverick logo, which makes a reference to Sigma, their leader.