Badass Creed/Fan Works

"We are the Ringbearers We are the light that drives back the darkness We are the wall that no evil can breach We are the staff and the sword that shall defend life We are the fire that will light the way to tomorrow Our Rings are Forever. We are Forever."
 * In the Daria Expanded Universe Fanfic series Tales of the Ringbearers, "The Ringbearer's Creed:"

"Our enemies fall, from low and high To salted earth, through burning sky And all shall know our Ringwraith's cry Let Vengeance Ring - and all hope die!"
 * Not to be outdone, those who wear the corrupted versions of the Rings - the Ringwraiths - have their own creed, which is infinitely more Badass:

"Yea verily, though I charge through the valley of the shadow of death, I shall fear no evil, for I am driving a house-sized mass of "fuck you.""
 * The Epic Tiberium Wars Fanfic has this from a Mammoth Tank crewman:

"We have sworn our lives in the service of the Brotherhood. In Brotherhood, we are all equal. Within our Brotherhood, we are united. Within unity, we are victorious. By attaining unity, we strive for peace. With our lives, we sacrifice to bring peace to the Brotherhood. Through our lives, we bring power to the Brotherhood. With power, the Brotherhood brings peace. Peace through power. In the name of Kane."
 * The Black Hand have their own, more solemn creed:

""I stand between the Light and the Darkness, between the Innocent and the Monstrous, between the Just and the Vile. I dwell at the edge of Darkness, that others may live in the Light. I am a Twilight Paladin. As such, I hereby take these oaths: "Upon my honor, upon my soul, upon my magic and my hope for redemption, I swear to never again kill a thinking being. "Upon my honor, upon my soul, upon my magic and my hope for redemption, I swear to seek and serve justice to the limit of my capacity and the best of my understanding. "Lastly, I swear my magic, my skills, and my life to your defense and your service.""
 * From Chapter 35 of Diashi Prime's Magical Girl Lyrical Nanoha Fanfic Endless Waltz comes what will become the Creed and Oaths of the Twilight Paladins:

""I am the Archangel of Solace, bound forever to those who wish not to go quietly into the night. I will not rest until it is assured that Existence is not damned to annihilation in the days of Ragnarok. So is my duty written, so shall it be.""
 * Chapter 12 of CSS.Stravag's Legend Of The Jokers Wild Revised has this:

"“In days of peace, in times of war, Protect our Queen forever more! The five Clouds stand, we are her Knights! To guard Hayate, our delight!”"
 * Shadow Crystal Mage's Takamachi Nanoha of 2814 has the Wolkenritter Oath, though so far only in the omake material and polls finally appearing in chapter 15:

""With Blood and Rage of crimson red, Ripped from a Corpse so freshly dead. Together with my hellish hate, I swear none other shall share my fate!""
 * Also, an altered Red Lantern Oath:

""I am the one who has been given a mission. Under the contract, release these powers. The winds are in the sky, the stars are in the heavens, the light is in my hands and the power is in my heart! And I shall shed my light over dark evil, for the dark things cannot stand the light, the light of the Green Lantern! Raging Heart Emerald Excelion, Set Up!" "Magical Girl Green Lantern, Zenryoku Zenkai! Ready for action!""
 * Later in the story, Nanoha's transformation aria takes a Level in Badass:
 * pose*

""Bring your thousands, I have my axe." "Bring your cannons, I have my armor." "Bring your mighty... I am my own champion." Cue Unit-01 ramming half the Lance of Longinus down Adam's head and a bemused Gendo, "Wrong end, son.""
 * An old Fanfiction by the name of Standing Tall from the now defunct site Second Impact hosted, quite possibly, one of the most Badass of Badass Creeds ever written; and it's delivered by Gendo Ikari of all people, to the face of a newly-restored Adam, describing human determination.

""If I am alone, why can I hear their voices?" "If I am a doll, why do I feel their tears?" "I am not alone. Shinji is my brother." "I am not a doll. Asuka is my sister." "My name is Rei." "A.YA.NA.MI. REI!""
 * Also, Rei reverse-mindfucking Lilith, when the skinny girl literally thrusts her belief in life into Lilith's core in addition to the Lance of Longinus.

""THOUGH I FACE THE SHADOWS OF THE WARP, I SHALL FEAR NO EVIL, I SHALL FEAR NO FOE! FOR I HAVE MOAR DAKKA THAN YOU, BITCHES!""
 * ToyHammer has this gem from a Space Marine the Badass Abnormal in a world of Warhammer 40,000, :

"From out of darkness comes a light. From out of Chaos comes a champion. To attack the innocent for your dark ambitions can never be forgiven. Judgment has been made-- and you are found wanting."
 * One of the Space Marine battle-brothers, though, does call out on the lack of sense of that last line.
 * From the incomplete Ranma ½/Sailor Moon fanfic Paragon by Rob "Kenko" Haynie, author of Girl Days:

"I swear to defend with my axe And to shield with my tin, The safety of the innocent that is more dear than my own, From the smallest insect to the greatest monarch. I protect the good from the wicked; so I must be pure of heart I defend the truth; so I must never lie. Standing guard so others may rest, I work and do not tire. I am prepared at any moment to give my life for those I protect. Despite the hardships this vow may bring, I take this oath freely, and with all my heart. I serve and protect the Land of Oz. I am a Tin Man."
 * The author of Zero Shock has posted a pair of Badass Creeds in the style of Archer's Unlimited Blade Works chant based around Jack's Bee Plasmid. They can be found here, for the first one that would be in the centerpiece of a Crowning Moment of Awesome, and here, which is a Crowning Moment of Funny in itself.
 * From the Tin Man fanfic Tin, there's the Tin Man Oath of Service:

"This Power is mine, this is my light, No-one can take what gives me Might, I claim to all within my Sight I want, I take, that is my Right."
 * "We're Power Rangers! We don't quit, we don't surrender, and most importantly, WE DON'T LOSE!!"
 * This troper read a fic where the main character's creed is "(I am) a fallen angel, a risen demon, a gargoyle guarding a church of sin and despair. I am vengeance made manifest. Nox Denticula. Night's fang. Dammed lot, stained with the blood of the innocent. I pronounce you guilty. And the guilty shall be punished for their crimes!"
 * Not literally from a fanfic, but the hypothetical Orange Lantern oath: