Ygra, Eater of All + Bartolome del Presidio + Camellia, the Seedmiser create an infinite loop that requires no mana.

Ygra turns all creatures into food. If you sacrifice a "food", Camellia creates a squirrel food. Bartolome sacrifices the squirrel food and gets a +1/+1 counter, and gives Ygra two +1/+1 counters. Camellia creates a new squirrel food. Repeat infinitely without spending mana.