Combat Celebrant + Kiki-Jiki, Mirror Breaker

Combat Celebrant
Kiki-Jiki, Mirror Breaker

Requires
All permanents on the battlefield.
Steps
  1. Activate Kiki-Jiki by tapping it, creating a token copy of Combat Celebrant with haste
  2. Proceed to your combat step
  3. Declare the Combat Celebrant copy as an attacker, choosing to exert it as it attacks
  4. The Combat Celebrant copy triggers, untapping all other creatures you control and causing you to get an additional combat phase after this one
  5. Repeat
Results
Infinite combat phases. Infinite creature tokens with haste. Infinite ETB. Infinite tap triggers.