This is my Whimsicott.
Whimsicott [M] @Big Root
Giga Drain- Heals more HP with the Big Root attatched.
Toxic- Slowly helps wear down the foe.
Leech Seed- Also help wear down the foe while also healing.
Calm Mind- Raises Def. and Sp Def.
I like to start out with a Leech Seed, So I can get health back every turn.
Then I raise my def. and sp. def. with Calm Mind, making it harder to deal damage on Whimsicott.
I then use toxic, poisonning my foe, also the poison deals more damage every turn.
Then I continue giga drainning, getting a lot of health back every turn.
I replaced calm mind with Twister, I have a Mew with my baton pass strategy.