Voltaic Construct + Tough Cookie + Prismatic Geoscope

Voltaic Construct

Tough Cookie

Prismatic Geoscope

How it works

1. Animate Prismatic Geoscope using Tough Cookie.
2. Activate Prismatic Geoscope by tapping it, adding at least three mana of any color
3. Activate Voltaic Construct by paying 2, untapping Prismatic Geoscope.
4. Repeat from step 2.

This clever loop turns your mana rocks into a self-sustaining engine by utilizing Tough Cookie's ability to turn noncreature artifacts into creatures, specifically transforming Prismatic Geoscope into a 4/4 artifact creature that can be targeted by abilities. Once animated, Prismatic Geoscope taps to produce at least three mana due to its domain ability, easily outstripping the cost to untap it. You then funnel that mana into Voltaic Construct to untap the Geoscope, leaving you with a net profit of mana and an infinite loop of colored mana and untaps for your artifact creatures.