Druids get a new ability in Mists of Pandaria called Symbiosis. It's the most interesting spell of the whole expansion and the mechanism behind it is very unique.
Here's the tooltip from WoWHead.
To offer a simple explanation: The druid creats a link with another player.The target player is granted ONE druid ability depending on his specialisation(healer would get a healing spell for example).The druid is granted ONE ability depending on the target's CLASS/Spec.
Another example: You are a restoration druid. Your target is a priest. Casting Symbiosis will grant you Leap of Faith. The priest will get Tranquility.
Spells gained by the druid:
|Death Knight||Blood||Frost & Unholy|
|Might of Ursoc||Wild Mushroom: Plague|
|Survival Instincts||Bear Hug||Entangling Roots ?|
|Priest||Discipline & Holy||Shadow|
|Shaman||Elemental & Enhancement||Restoration|
|Warrior||Arms & Fury||Protection|
|Stampeding Shout|| Savage Defense ? |
To understand the ability's full potential, watch the video below: