The Big Top

{T}: Add one mana of any color that appears on your top. (A top is an outerwear garment worn on the upper body.)

Island

Liquimetal Torque

{T}: Add {C}.
{T}: Target nonland permanent becomes an artifact in addition to its other types until end of turn.

Seat of the Synod

Razortide Bridge

Razortide Bridge enters tapped.
Indestructible
{T}: Add {W} or {U}.

Mirrodin Besieged

As Mirrodin Besieged enters, choose Mirran or Phyrexian.
• Mirran — Whenever you cast an artifact spell, create a 1/1 colorless Myr artifact creature token.
• Phyrexian — At the beginning of your end step, draw a card, then discard a card. Then if there are fifteen or more artifact cards in your graveyard, target opponent loses the game.

Thopter Spy Network

At the beginning of your upkeep, if you control an artifact, create a 1/1 colorless Thopter artifact creature token with flying.
Whenever one or more artifact creatures you control deal combat damage to a player, draw a card.

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.

Thought Monitor

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
Flying
When Thought Monitor enters, draw two cards.

Kindly Cognician

Spells you cast that refer to artifacts or Contraptions in their rules text cost {1} less to cast.

Ancient Den

Scrap Trawler

Whenever Scrap Trawler or another artifact you control is put into a graveyard from the battlefield, return to your hand target artifact card in your graveyard with lesser mana value.

Thopter Foundry

{1}, Sacrifice a nontoken artifact: Create a 1/1 blue Thopter artifact creature token with flying. You gain 1 life.

Emry, Lurker of the Loch

This spell costs {1} less to cast for each artifact you control.
When Emry, Lurker of the Loch enters, mill four cards.
{T}: Choose target artifact card in your graveyard. You may cast that card this turn. (You still pay its costs. Timing rules still apply.)

Shorikai, Genesis Engine

{1}, {T}: Draw two cards, then discard a card. Create a 1/1 colorless Pilot creature token with "This creature crews Vehicles as though its power were 2 greater."
Crew 8 (Tap any number of creatures you control with total power 8 or more: This Vehicle becomes an artifact creature until end of turn.)
Shorikai, Genesis Engine can be your commander.