Note: This spell was removed from the game in patch 6.0.2 for being too complex/convoluted.  Considering that I was able to make an entire blog post just out of explaining what one single spell did, I think this is a reasonable claim.

Symbiosis is a new ability granted to the Druid class in Mists of Pandaria.  When cast on another player by a Druid, both players are given access to one of each other’s spells for an hour, depending on both the druid’s spec and the recipient’s role.  The spells exchanged are not exactly like their original forms, but are similar (read the tooltips for details).  Both players still retain their granted abilities, as well (eg, you don’t lose spell reflect just because the druid gained it).

Because I often see people who aren’t sure what class or spec grants what (both the giver and recipient’s specs influence what abilities are exchanged) — including many druids — I thought I would offer a summary for people to use as a reference.  I have sorted by class for convenience:

Rogues

Gives to Druid
• Redirect to cat
• Feint to bear
• Evasion to tree
• Cloak of Shadows to moonkin

Receives from Druid
• Growl

Death Knight

Gives to Druid
• Death Coil to cat
• Bone Shield to bear
• Icebound Fortitude to tree
• Anti-Magic Shell to moonkin

Receives from Druid
• Wild Mushroom: Plague as Frost & Unholy
• Might of Ursoc as Blood

Warrior

Gives to Druid
• Shattering Blow to cat
• Spell Reflect to bear
• Intimidating Roar to tree
• Intervene to moonkin

Receives from Druid
• Stampeding Shout as Arms & Fury
• Savage Defense as Protection

Paladin

Gives to Druid
• Divine Shield to cat
• Consecration to bear
• Cleanse to tree
• Hammer of Justice to moonkin

Receives From Druid
• Wrath as Retribution
• Barkskin as Protection
• Rebirth as Holy

Monk

Gives To Druid
• Clash to cat
• Elusive Brew to bear
• Fortifying Brew to tree
• Grapple Weapon to moonkin

Receives From Druid
• Bear Hug as Windwalker
• Entangling Roots as Mistweaver
• Survival Instincts as Brewmaster

Shaman

Gives to Druid
• Feral Spirit to cat
• Lightning Shield to bears
• Spiritwalker’s Grace to tree
• Purge to moonkin

Receives From Druid
• Solar Beam as Elemental & Enhancement
• Prowl as Restoration

Mage

Gives to Druid
• Frost Nova to cat
• Frost Armor to bear
• Iceblock to tree
• Mirror Image to moonkin

Receives from Druid
• Healing Touch

Warlock

Gives to Druid
• Soul Swap to cat
• Life Tap to bear
• Demonic Circle: Teleport to tree
• Unending Resolve to moonkin

Receives From Druid
• Rejuvenation

Priest

Gives To Druid
• Dispersion to cat
• Fear Ward to bear
• Leap of Faith to tree
• Mass Dispel to moonkin

Receives From Druid
• Tranquility as Shadow
• Cyclone as Holy & Discipline

Hunter

Gives to Druid
• Play Dead to cat
• Ice Trap to bear
• Deterrence to tree
• Misdirection to moonkin

Receives from Druid
• Dash