Animation Module + Sigil Captain + Phyrexian Altar

Animation Module

Sigil Captain

Phyrexian Altar

How it works

1. Put a +1/+1 counter on a creature you control.
2. Animation Module triggers, causing you to pay 1 to create a 1/1 Servo artifact creature token.
3. When the Servo enters the battlefield, Sigil Captain triggers, putting two +1/+1 counters on the Servo.
4. Animation Module triggers, holding priority, activate Phyrexian Altar by sacrificing the Servo, adding 1.
5. Resolve the Animation Module trigger, causing you to pay 1 to create a 1/1 Servo artifact creature token.
6. Repeat from step 3.