As the first American dragon, Jake Long (American Dragon: Jake Long) is chosen to protect the underground magical world of New York, using his ability to transform into a powerful dragon to do so.
Being next in the Avatar Cycle, Aang (Avatar: The Last Airbender) is chosen to maintain balance of the world. To do so, he is required to master the element of air, water, earth, and fire, as well as control the Avatar State, where he is at his most powerful.
As the Avatar after Aang, Korra (The Legend of Korra) is chosen to maintain the balance of the world of man and spirit.
The Legendary Bladers (Beyblade Metal Fury) are a group of bladers that carry a piece of the Star Fragment enchanted inside their Beyblades and have destined to defeat the God of Destruction, Nemesis.
The Toa (Bionicle) are heroes chosen to protect the universe from evil.
As the Slayer, Buffy Summers (Buffy the Vampire Slayer) exists to battle the supernatural forces of evil and save the human race.
As a servant of the Powers That Be, Angel (Buffy the Vampire Slayer/Angel) is dedicated to serving them and helping the helpless.
The Charmed Ones (Charmed) are the three most powerful witches in the world, dedicated to protecting the innocent and ridding the world of evil.
The Green Lantern Corps (DC Comics) have existed for billions of years, sworn to protect the universe, and given special rings in order to do so.
Though at first apathetic to his destiny, Dante (Devil May Cry series) placed the heavy burden of taking his father's place as the savior of the humans on himself, willing to protect them from the countless demonic forces that plague his world.
The DigiDestined (Digimon series) are benevolent children who are chosen to protect the the Digital World and given a Digivice, Digimon partner, and often powers in order to do so.
Kami (Dragon Ball) is one of many previous guardians of earth ...
... and Dende is the current one.
Zed (Kiba - Anime) was chosen for the most powerful key spirit, Amil Gaoul to end the fights between the nations.
Pit (Kid Icarus) is Palutena's most loyal servant and trusted bodyguard. He is often tasked of guarding her and the human race from the wicked forces of Medusa and the Underworld.
Sora (Kingdom Hearts series) is one of the wielders of the sacred Keyblades.
Zane (Lego Ninjago: Masters of Spinjitzu), White Ninja of Ice.
Cole (Lego Ninjago: Masters of Spinjitzu), Black Ninja of Earth.
Jay (Lego Ninjago: Masters of Spinjitzu) Blue Ninja of Lightning.
Kai (Lego Ninjago: Masters of Spinjitzu), Red Ninja of Fire.
Lloyd Garmadon (Lego Ninjago: Masters of Spinjitzu), Green Ninja of Energy, destined to become the Ultimate Spinjitzu Master.
X (Megaman X series) was the last creation of Dr. Thomas Light. Unlike most robots at the time of his creation, X possessed the ability to worry, grow, and make his own decisions with no programming to do so. This in turn allows X to tap into his "limitless potential". Because of this, Dr. Light believed X to be the one true hope of the world.
The Mane Six (My Little Pony: Friendship is Magic) are the embodiments of the Elements of Harmony. As such, they represent the elements of honesty, kindness, laughter, generosity, loyalty, and magic in order to protect harmony in all of Equestria.
Naruto Uzumaki (Naruto series) was one of the Children of the Prophecy who were foretold to hold the fate of the world in their hands. Due to being the reincarnation of Hagoromo Ōtsutsuki's son, Asura, Naruto was predicted to complete the sealing of Kaguya Ōtsutsuki and save the world
Sasuke Uchiha (Naruto series) was one of the Children of the Prophecy who were foretold to hold the fate of the world in their hands. Due to being the reincarnation of Hagoromo Ōtsutsuki's son, Indra, Sasuke was predicted to complete the sealing of Kaguya Ōtsutsuki and save the world.
Ryu Hayabusa (Ninja Gaiden series) is the current Dragon Ninja of the Dragon Lineage. Like the 13 Dragons before him, his duty is to protect the world from the Fiends. To combat this evil, Ryu is trained in multiple forms of combat, weaponry, spiritual practices, and is armed with the divine Dragon Sword.
Despite their improper morals and rude behavior, Panty and Stocking (Panty and Stocking with Gaterbelt) are angels from Heaven chosen to guard Daten City from evil spirits and ghosts. When they're not bickering with each other, they're nearly unstoppable.
Celebi (Pokémon) is the Guardian of the Forest.
For 800 years the town of Norrisville has been protected from evil by a ninja. Every four years a new ninja is chosen, and Randy Cunningham (Randy Cunningham: 9th Grade Ninja) is chosen as the new ninja to protect Norrisville from the evil plans of the Sorcerer.
Sailor Pluto (Sailor Moon) is the guardian of the Door of Time.
Knuckles the Echinda (Sonic The Hedgehog) is the last of his kind, sworn to protect the sacred Master Emerald from anything that can harm it.
Blaze the Cat (Sonic the Hedgehog seires) is a princess from alternate dimension, and guardian of the Sol Emeralds.
The Soul Riders (Starshine Legacy) are young women chosen by faith to protect the island of Jorvik from dark forces.
After being chosen and gifted with the Power Primate, Chiro (Super Robot Moneky Team Hyper Force Go!) became to the new leader of the Super Robot Monkey Team. As such, he leads the Hyper Force: Antauri, Mr. Hal Gibson, SPRX-77, Otto, and Nova to protect Shugazoom City and the universe from the evil of the Skeleton King.
Juniper Lee (The Life and Times of Juniper Lee) is the Te Xuan Ze, protector of the balance between the human an magical worlds in the City of Orchid Bay. To preserve this balance, she is magically enhanced, making her stronger and faster than the average human,and is capable of using magic.
Jim Lake (Trollhunters) was chosen to be the new Trollhunter, the warrior who protects the world from evil trolls and goblins.
Hellgate (Valkyrie Crusade) is the embodiment and the guardian of the hell's gate.
Necronomicon (Valkyrie Crusade) is the embodiment and the guardian of necronomicon.
Hermit (Valkyrie Crusade) is the guardian of infinite space.
Kjersti (Valkyrie Crusade) the guardian goddess of children.
The five Guardians of the Veil (W.I.T.C.H.) are a group of magical warriors gifted with the abilities of Quintessence, Water, Fire, Earth, and Air with the mission to protect Kandrakar, the center of the universe.
Omi, Raimundo, Clay, and Kimiko (Xiaolin Showdown) are the chosen Xiaolin Dragons of the water, wind, earth, and fire respectively. Together they are sworn to gather all of the Shen Gong Wu before the evil Heylin Witch, Wuya, who seeks to throw the world into 10,000 years of darkness.
The Signers (Yu-Gi-Oh 5D) are chosen by the Crimson Dragon to protect the world of the forces of darkness.