Alright, so. The topic really states it all.
When you're doing the Amphitheatre of Anguish (Equivalent to Ring of Blood in Nagrand) in Zul'drak.
On the last boss, he jumps off his mammoth. After he has done that, get on it really fast. And just sprint out the arena, just run like hell.
The boss resets (I think?) and you get to keep the mount, for your own enjoyment. Although, the mount has a duration-time.
After the duration-time is gone, you have around 1-3 seconds interval from climbing up on it again, resetting the duration-time.
So basicly, you get to keep that mount forever.
For what reason? I don't know, chain-stunning people is funz.
---------- Post added at 02:25 PM ---------- Previous post was at 02:11 PM ----------
You can also give it to your friends, and let them bash mobs with it and still get 100% xp. I made another reply, since I can't edit, apparently.