Changeling Hero

Changeling (This card is every creature type.)
Champion a creature (When this enters, sacrifice it unless you exile another creature you control. When this leaves the battlefield, that card returns to the battlefield.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

The List

Lorwyn

Changeling (This card is every creature type at all times.)
Champion a creature (When this comes into play, sacrifice it unless you remove another creature you control from the game. When this leaves play, that card returns to play.)
Lifelink (Whenever this creature deals damage, you gain that much life.)