This one is widely known but I'll share it anyway.
If you leave a battleground while you have dots on you and are close to dying, they won't get removed when you leave, so when you get where you queued from, if you get no heals, you will die.
I always do this when we are losing in arenas so that they don't get a killing blow on me.6):
Useless but you at least get some laughs nonetheless.