Quakers, Mennonites, Hare Krishna believers... the list of pacifistic religions is pretty long. The word "Islam" for example actually means "Peace".
But these religions also frequently allow for the possibility of war and violence, for the purpose of defending ourselves.
"The central principle of Pacifism is to avoid unnecessary violence, which by its very definition means that violence is sometimes necessary to defend the weak and the innocent." - Charles Moffat.
At its core Pacifism is all about not being a bully, a brute and a savage who just takes what they want and does what they want. Pacifism is about being honourable, courageous and choosing not to fight when there is no need to fight.
In Pop Culture we can refer to the Superman principle: "Superman doesn't kill." Ever. Oh sure, he may have wrecked a robot or several in his time, but they were always unintelligent automatons. Superman has never actually killed a living / thinking entity.
But that hasn't stopped him from fighting crime and super villains. The Pacifism principle isn't limited to Superman either, it is a trait common to many principled superheroes in comic books (althought obviously not Wolverine).
The 9 Principles of a True Pacifist
#1. Never kills or attacks an unarmed foe.
#2. Never harms an innocent.
#3. Never tortures for any reason.
#4. Never kills for pleasure.
#5. Always defends the weak and innocent.
#6. Works within the boundaries of the law when possible.
#7. Avoids breaking the law except in rare desperate circumstances.
#8. Believes in self-discipline (ie. controlling your temper).
#9. Never deliberately abuses their position or other people.
Contrary to what some people might think however, this doesn't mean a pacifist should be ignorant of the martial arts. Quite the opposite, if you look at #5 pacifists are expected to defend the weak and innocents and thus a knowledge of how to defend oneself and others is necessary.
Bodyguards, peace keepers, anyone who works in the defense of others should be respected as pacifists, but most importantly they must not abuse their authority (ie. police brutality).
Civil rights leader Malcolm X for example is a good example of pacifism at work. He believed people should behave with honour and integrity, but he also believed people have the right to defend themselves and others.
Some people might think this means pacifism is all black and white. For the most part this is correct, but there is some grey areas... for example torture could be seen as a necessity in dire circumstances, but only if it can proven that the person being tortured actually possesses the knowledge which can be used to save people. Torturing someone without proof that they possess such knowledge, torturing for the purpose of pleasure, and likewise torturing someone out of anger and revenge is contradictory to the principles of pacifism.
“My pacifism is an instinctive feeling, a feeling that possesses me because the murder of men is disgusting. My attitude is not derived from any intellectual theory but is based on my deepest antipathy to every kind of cruelty and hatred.” - Albert Einstein.