Reclusive Artificer

Haste (This creature can attack and {T} as soon as it comes under your control.)
When this creature enters, you may have it deal damage to target creature equal to the number of artifacts you control.

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.

Shrapnel Blast

As an additional cost to cast this spell, sacrifice an artifact.
Shrapnel Blast deals 5 damage to any target.

Shambling Suit

Shambling Suit's power is equal to the number of artifacts and/or enchantments you control.

Silverbluff Bridge

This land enters tapped.
Indestructible
{T}: Add {U} or {R}.

Mountain

Island

Memnite

Steel Overseer

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

Third Path Iconoclast

Whenever you cast a noncreature spell, create a 1/1 colorless Soldier artifact creature token.

Accorder's Shield

Equipped creature gets +0/+3 and has vigilance. (Attacking doesn't cause it to tap.)
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Feedback Bolt

Feedback Bolt deals damage to target player or planeswalker equal to the number of artifacts you control.

Concussive Bolt

Concussive Bolt deals 4 damage to target player or planeswalker.
Metalcraft — If you control three or more artifacts, creatures controlled by that player or by that planeswalker's controller can't block this turn.

Hellkite Igniter

Flying, haste
{1}{R}: This creature gets +X/+0 until end of turn, where X is the number of artifacts you control.

Galvanic Blast

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