Sai, Master Thopterist + Myr Retriever + Scrap Trawler + Ashnod's Altar

Sai, Master Thopterist
Myr Retriever
Scrap Trawler
Ashnod's Altar

Requires
Myr Retriever in your graveyard. All other permanents on the battlefield.
Steps
  1. Activate Ashnod's Altar by sacrificing Scrap Trawler, adding cc
  2. When Scrap Trawler dies, it triggers, returning Myr Retriever from your graveyard to your hand
  3. Cast Myr Retriever by paying 2
  4. Sai triggers, creating a 1/1 Thopter artifact creature token
  5. Activate Ashnod's Altar twice by sacrificing the Thopter and Myr Retriever, adding cccc
  6. When Myr Retriever dies, it triggers, returning Scrap Trawler from your graveyard to your hand
  7. Cast Scrap Trawler by paying 3
  8. Sai triggers, creating a 1/1 Thopter artifact creature token
  9. Repeat
Results
Infinite creature tokens. Infinite colorless mana. Infinite ETB. Infinite LTB. Infinite death triggers. Infinite sacrifice triggers. Infinite storm count.