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 Cataclysm 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. Initially, faction capitals could not be championed in instances that were already connected to a specific faction, such as those introduced in The Burning Crusade expansion. As of patch 4.3, faction capital reputation can also be championed in 5-man Burning Crusade dungeons, though under slightly different rules from those in Azeroth.

The reputation gained in The Burning Crusade dungeons is in addition to the normal Outland faction reputation gain, so the player improves his or her standing with two factions at once. The reputation gain follows the same rules as those for the host faction; since Hellfire Ramparts grants Honor Hold or Thrallmar reputation until one point short of Honored, wearing a home city tabard in that instance grants Alliance or Horde reputation, improving all capital reputations until one point short of Honored. Level 70 and Heroic dungeons give reputation for both the Outland faction and the capital city through Exalted.

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. Wearing any championed faction's tabard, even the tabard for a Cataclysm faction that cannot be championed in a level 80 dungeon, will prevent Horde Expedition or Alliance Vanguard reputation gain. Heroic mode dungeons will provide a small increase to the rate of reputation gain. Normal-mode dungeons prior to level 80, such as Utgarde Keep or The Nexus, behave the same way as old-world dungeons; the player may champion the capital cities, but will not gain reputation with any group by default.

Dungeons intended for players above level 80 (i.e. those from Cataclysm and Mists of Pandaria) do not award any reputation for these factions even if the tabard is worn. This behavior differs from that of the tabards introduced in Cataclysm.

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

Additionally, dungeons intended for players above level 85 (i.e. those from Mists of Pandaria) do award reputation for these factions if the tabard is worn. This behavior differs from that of the tabards introduced in Wrath of the Lich King.

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.