Blowfly Infestation + Hapatra, Vizier of Poisons

Prerequisites

You control at least two other creatures with toughness equal to one. You have a way to put a -1/-1 counter on a creature.

Steps

1. Put a -1/-1 counter on any creature you control with toughness equal to one.
2. The creatue dies as a state-based action due to having zero toughness.
3. Hapatra and Blowfly Infestation trigger.
4. Resolve the Hapatra trigger, creating a 1/1 Snake creature token.
5. Resolve the Blowfly Infestation trigger, putting a -1/-1 counter on any creature you control with toughness equal to one.
6. Repeat from step 2.