Combat Celebrant + Helm of the Host

Combat Celebrant
Helm of the Host

Requires
All permanents on the battlefield. Helm of the Host attached to Combat Celebrant.
Steps
  1. At the beginning of your combat phase, Helm of the Host triggers, creating a token copy of Combat Celebrant with haste
  2. Declare the token Combat Celebrant as an attacker choosing to exert it as it attacks
  3. The Combat Celebrant copy triggers, untapping all other creature you control and causing you to get an additional combat phase after this one
  4. Repeat
Results
Infinite combat phases. Infinite tapped creature tokens. Infinite ETB. Infinite untap of creatures you control.