Myr Enforcer

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)

Mishra's Factory

{T}: Add {C}.
{1}: Mishra's Factory becomes a 2/2 Assembly-Worker artifact creature until end of turn. It's still a land.
{T}: Target Assembly-Worker creature gets +1/+1 until end of turn.

Frogmite

Cranial Plating

Equipped creature gets +1/+0 for each artifact you control.
{B}{B}: Attach Cranial Plating to target creature you control.
Equip {1}

Spined Thopter

({U/P} can be paid with either {U} or 2 life.)
Flying

Ensoul Artifact

Enchant artifact
Enchanted artifact is a creature with base power and toughness 5/5 in addition to its other types.

Etched Champion

Metalcraft — Etched Champion has protection from each color as long as you control three or more artifacts.

Spatial Contortion

({C} represents colorless mana.)
Target creature gets +3/-3 until end of turn.

Tormod's Crypt

{T}, Sacrifice Tormod's Crypt: Exile target player's graveyard.

Signal Pest

Battle cry (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn.)
Signal Pest can't be blocked except by creatures with flying or reach.

Darksteel Citadel

Shared Discovery

As an additional cost to cast this spell, tap four untapped creatures you control.
Draw three cards.

Island

Ornithopter

Vault of Whispers

Tomb of the Spirit Dragon

{T}: Add {C}.
{2}, {T}: You gain 1 life for each colorless creature you control.

Gingerbrute

Haste
{1}: Gingerbrute can't be blocked this turn except by creatures with haste.
{2}, {T}, Sacrifice Gingerbrute: You gain 3 life.

Welding Jar

Sacrifice Welding Jar: Regenerate target artifact.

Porcelain Legionnaire

({W/P} can be paid with either {W} or 2 life.)
First strike

Metallic Rebuke

Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Counter target spell unless its controller pays {3}.

Aether Spellbomb

{U}, Sacrifice Aether Spellbomb: Return target creature to its owner's hand.
{1}, Sacrifice Aether Spellbomb: Draw a card.