Sneak Attack and Tradewind Rider on the battlefield.
Creatures you control can tap to produce at least ({1} magic symbol) ({R} magic symbol) .
You control at least one additional creature.
Tradewind Rider does not have summoning sickness.
Steps
Activate all mana producing creatures you control by tapping them, adding at least ({1} magic symbol) ({R} magic symbol) .
Activate Sneak Attack by paying ({R} magic symbol) , putting Great Oak Guardian from your hand onto the battlefield.
Great Oak Guardian enters the battlefield, untapping all creatures you control and giving them +2/+2 until end of turn.
Activate Tradewind Rider by tapping it, Great Oak Guardian, and one other creature you control, returning Great Oak Guardian from the battlefield to your hand.
Repeat.
Results
Infinite ETB.
Infinite LTB.
Infinitely large creatures until end of turn.
Infinite mana creatures you control can produce.
Infinite untap of creatures you control.
Infinitely large creatures you control until end of turn.