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.

Master of Etherium

Master of Etherium's power and toughness are each equal to the number of artifacts you control.
Other artifact creatures you control get +1/+1.

Darksteel Citadel

Rest in Peace

When Rest in Peace enters, exile all graveyards.
If a card or token would be put into a graveyard from anywhere, exile it instead.

Etched Champion

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

Spellskite

{U/P}: Change a target of target spell or ability to Spellskite. ({U/P} can be paid with either {U} or 2 life.)

Ancient Grudge

Destroy target artifact.
Flashback {G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Vault Skirge

({B/P} can be paid with either {B} or 2 life.)
Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Memnite

Inkmoth Nexus

{T}: Add {C}.
{1}: Inkmoth Nexus becomes a 1/1 Phyrexian Blinkmoth artifact creature with flying and infect until end of turn. It's still a land. (It deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)

Glimmervoid

At the beginning of the end step, if you control no artifacts, sacrifice Glimmervoid.
{T}: Add one mana of any color.

Galvanic Blast

Galvanic Blast deals 2 damage to any target.
Metalcraft — Galvanic Blast deals 4 damage instead if you control three or more artifacts.

Ornithopter

Mountain

Relic of Progenitus

{T}: Target player exiles a card from their graveyard.
{1}, Exile Relic of Progenitus: Exile all graveyards. Draw a card.

Cranial Plating

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

Mox Opal

Metalcraft — {T}: Add one mana of any color. Activate only if you control three or more artifacts.

Leyline of Sanctity

If Leyline of Sanctity is in your opening hand, you may begin the game with it on the battlefield.
You have hexproof. (You can't be the target of spells or abilities your opponents control.)

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Steel Overseer

{T}: Put a +1/+1 counter on each artifact creature you control.

Whipflare

Whipflare deals 2 damage to each nonartifact creature.

Springleaf Drum

{T}, Tap an untapped creature you control: Add one mana of any color.

Island

Blinkmoth Nexus

{T}: Add {C}.
{1}: Blinkmoth Nexus becomes a 1/1 Blinkmoth artifact creature with flying until end of turn. It's still a land.
{1}, {T}: Target Blinkmoth creature gets +1/+1 until end of turn.

Thoughtcast

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

Arcbound Ravager

Sacrifice an artifact: Put a +1/+1 counter on Arcbound Ravager.
Modular 1 (This creature enters with a +1/+1 counter on it. When it dies, you may put its +1/+1 counters on target artifact creature.)

Thoughtseize

Target player reveals their hand. You choose a nonland card from it. That player discards that card. You lose 2 life.