Championing

Championing is a system for customized reputation gains from dungeons, introduced in World of Warcraft: Wrath of the Lich King. Killing a monster that yields reputation inside a dungeon while wearing a particular faction's tabard will grant reputation with that faction; it allows a player to acquire reputation in a dungeon with a faction other than that normally associated with the dungeon.

The tabards that allow championing can be acquired at reputation with their respective factions.

Factions that can be championed
Only some factions can be championed.

Faction Capitals
Following the Shattering in Patch 4.0.3a, it is now possible to champion the faction capitals in dungeons of any level by purchasing an applicable tabard from the faction Quartermaster. The only dungeons not eligible are those which grant rep for a specific faction already, such as most instances introduced in The Burning Crusade expansion.

Wrath of the Lich King
Dungeons introduced in the Wrath of the Lich King expansion that are intended for level 80 players, including certain normal mode dungeons and all heroic mode dungeons, are eligible for championing the following factions:
 * Argent Crusade
 * Kirin Tor
 * Knights of the Ebon Blade
 * Wyrmrest Accord

If you do not wear a champion tabard, you may gain reputation with either the Horde Expedition or the Alliance Vanguard. Heroic mode dungeons will provide a small increase to the rate of reputation gain.

Cataclysm
Dungeons introduced in the Cataclysm expansion that are intended for level 85 players, including most normal mode dungeons and all heroic mode dungeons, are eligible for championing the following factions:
 * Therazane
 * Guardians of Hyjal
 * Earthen Ring
 * Ramkahen
 * Dragonmaw clan
 * Wildhammer clan

Reputation Per Dungeon
The following tables outline the amount of reputation that may be earned toward a faction during a full clear of each dungeon.

Note: Values in the above table were gathered from Wowpedia or Wowhead and may not be 100% accurate.