Valkyrie's Call + Amoeboid Changeling + Spawning Pit + Pestermite

Valkyrie's Call

Amoeboid Changeling

Spawning Pit

Pestermite

How it works

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