Valkyrie's Call + Amoeboid Changeling + Spawning Pit + Little Bear

Valkyrie's Call

Amoeboid Changeling

Spawning Pit

Little Bear

How it works

1. Activate Amoeboid Changeling's second ability by tapping it, removing all creature types from Little Bear.
2. Activate Spawning Pit by sacrificing Little Bear.
3. When Little Bear dies, Valkyrie's Call triggers, returning Little Bear from your graveyard to the battlefield as an Angel with flying and a +1/+1 counter on it.
4. When Little Bear enters the battlefield, it triggers, untapping Amoeboid Changeling.
5. Resolve the Spawning Pit ability, putting a charge counter on it.
6. Repeat.