+60% damage to beasts for hunter and lock pets.

In the Jade forest there are 2 elite tigers (Ruukti and Ro'shen) that give a debuff called master stalker which increases damage against beasts by 20% per stack to whoever deals the killing blow. This can stack up to 3 times and lasts 2 minutes.

Lock pets can simply kill 3 of these tigers and hit 3 stacks, then presumably be pulled out in a raid or on whatever beast you want to get a bonus on. You simply need to dismiss the pet in between tiger kills and make sure the PET gets the killing blow.

For hunters it's a bit more difficult but potentially more rewarding. To avoid having the debuff wiped from the pet while summoning it back, you need the HUNTER to also have the debuff on him. This behavior is new to the 6.0 debuff system changes and is likely unintended. So you can potentially stack an entire stampede team with this debuff, but you will need the hunter to have the debuff on him when you use the stampede. The debuff can be zoned with, but I have not gone into an instance, just my garrison, so it's not 100% tested yet. That said, I can find no reason this wouldn't work in a raid if you got a summon just before engaging the boss. Locks can just whip out their pet of choice, though it's probably only worth it for Demo.