Leonardo, Sewer Samurai + Solemnity + Blasting Station + Ornithopter

Leonardo, Sewer Samurai

Solemnity

Blasting Station

Ornithopter

How it works

1. Activate Blasting Station by tapping it and sacrificing Ornithopter.
2. Cast Ornithopter from your graveyard by paying 0. It will not enter with a finality counter on it due to Solemnity.
3. When Ornithopter enters, Blasting Station triggers, untapping Blasting Station.
4. Repeat.

This loop lets you repeatedly turn a zero-mana artifact creature into infinite damage and triggers by exploiting a clever replacement effect interaction. With Solemnity on the battlefield preventing counters from being placed on permanents, Leonardo, Sewer Samurai's drawback of putting a finality counter on creatures cast from your graveyard is completely negated. This allows you to endlessly replay Ornithopter straight from your graveyard using Leonardo's permission, feeding it directly back into Blasting Station's sacrifice and untap loop to blast your opponents away.