Found this earlier while doing some AV, May be common knowledge to some but i am sure there are people not aware of this quest as well as how much XP it gives at the moment.
The quest: Proving Grounds
Given by: Lieutenant Haggerdin (Alliance)
Given by: Warmaster Laggrond (Horde)
These quest givers are located south of Ruins of Alterac in Hillsbrad Foothills.
Once you accept the quest que up for Alterac Valley (battleground) and collect your factions banner by going into the cave, now here is where some extra XP comes in. Completing this quest gives you Frostwolf Insignia Rank 1 or Stormpike Insignia Rank 1 and once you acquire these you can then instantly turn it in at the same location without having to do anything 5 times to upgrade it to the EPIC rank 6 version of the trinket.
Each quest turn in was giving roughly 130,000-180,000 which is about 750,000-900,000 XP for doing 1 AV
Not game breaking but a nice bump to someone trying to get some extra XP while they grind AV. Also a good idea while your doing this quest to grab the others in the cave which are very easy for example assault a graveyard, which will help boost your total xp from the BG.
The trinket upgrades do require rep up to exalted for the epic trinket, with AV it is fairly easy to get exalted.