This is an exploit i found when i was leveling my priest.
I was doing the quest in Dragonblight where you're supposed to fly and "pick up" the crazy villagers, unfortunately I do not know the name of the specific quest.
This quest is alliance only, but it might work with horde equal ones.
The mechanic for theese mounts you use meanwhile you're doing the quest is that you have to stay in the quest zone to not get dismounted, but. You will get dismounted after about 15 seconds.
Step 1. Queue up for a battleground, I queued to Warsong Gulch.
Step 2. When the queue pops, use the loaned mount and when you're mounted, join the bg.
When you get into the battleground, depending on your computer/internet, you will be on a mount for a certain time, between 15-> 0 seconds.
You can by your own imagine the things you can do with this.