This is my first real post here, so I'll start out with a disclaimer that this is half repost and (from what i can tell) half original content. I can't take credit for the bulk of this exploit, which is how to get underneath Shattrath, but after searching a fair few times I haven't seen it used this way before.
The payload of this exploit is to cause up to 40 players of your own faction to take 10% durability damage.
1) Get underneath shattrath. (the repost part) As a rogue, druid or warrior scare the chickens in southern shattrath so that they run away (druids- demo roar, warriors- demo shout, rogues- don't know, sorry =P) into the wall. When one of the chickens has run into the wall, feral charge/charge/shadowstep the chicken to pass through the wall into the glitchy underside of shat.
2) Mount up on your flying mount (flight form doesn't work, the model's too small) and fly over to where your battlemaster is, remaining underneath the ground.
3) Advertise that you're forming an awesome premade and spam invite your least favourite people =D.
4) Fly over to this position and slowly rise up on your mount until your head is only just above ground. Make sure the game still thinks you're flying and queue as a group.
5) Drop back underneath the ground, wait for the queue to pop. Don't join the bg and enjoy your front row seat of people reappearing underneath shat at the exact point you queued and falling to their death.
Not especially useful, but can help to get back at people who've pissed you off or just for a few laughs when you're bored.