Not an especially useful exploit, but right now there is a bug that causes your Headless Horseman mount(also probably celestial steed and other ground/flying mounts) to start flying after exiting a random battleground or dungeon if you entered the random standing anywhere in Dalaran while on the mount(the dismount timer starts as soon as you exit). Youtube link to demonstrate.
edit: cropped out my name, let me know if you can still see it somewhere