Mirran Spy

Flying
Whenever you cast an artifact spell, you may untap target creature.

Drumbellower

Flying
Untap all creatures you control during each other player's untap step.

Clock of Omens

Tap two untapped artifacts you control: Untap target artifact.

Seat of the Synod

Voyager Quickwelder

Artifact spells you cast cost {1} less to cast.

Etherium Sculptor

Mendicant Core, Guidelight

Mendicant Core's power is equal to the number of artifacts you control.
Start your engines! (If you have no speed, it starts at 1. It increases once on each of your turns when an opponent loses life. Max speed is 4.)
Max speed — Whenever you cast an artifact spell, you may pay {1}. If you do, copy it. (The copy becomes a token.)

Intruder Alarm

Creatures don't untap during their controllers' untap steps.
Whenever a creature enters, untap all creatures.

Mycosynth Golem

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Artifact creature spells you cast have affinity for artifacts. (They cost {1} less to cast for each artifact you control.)

Darksteel Citadel

Foundry Inspector

Ancient Den

Unwinding Clock

Untap all artifacts you control during each other player's untap step.

Belisarius Cawl

Ultima Founding — {T}, Tap two untapped artifacts you control: Create a 2/2 white Astartes Warrior creature token with vigilance.
Master of Machines — {T}, Tap X untapped creatures you control: Look at the top X cards of your library. You may reveal an artifact card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.