Ashnod's Altar, and Railway Brawler

Prerequisites

• Ashnod's Altar on the battlefield
• Railway Brawler on the battlefield

Steps

1. Activate Ashnod's Altar by sacrificing the persist creature
2. When the persist creature dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it
3. When the persist creature enters, Railway Brawler triggers, putting a number of +1/+1 counters on the persist creature
4. Repeat

Results

• Infinite ETB
• Infinite LTB
• Infinite colorless mana
• Infinite death triggers
• Infinite sacrifice triggers