Galvanic Blast

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

Goblin Gaveleer

Hexgold Sledge

Trample
This creature gets +2/+0 for each Equipment attached to it.

Hoard-Smelter Dragon

Flying
{3}{R}: Destroy target artifact. This creature gets +X/+0 until end of turn, where X is that artifact's mana value.

Koth of the Hammer Emblem

Koth of the Hammer

+1: Untap target Mountain. It becomes a 4/4 red Elemental creature until end of turn. It's still a land.
−2: Add {R} for each Mountain you control.
−5: You get an emblem with "Mountains you control have '{T}: This land deals 1 damage to any target.'"

Kuldotha Phoenix

Flying, haste
Metalcraft — {4}: Return this card from your graveyard to the battlefield. Activate only during your upkeep and only if you control three or more artifacts.

Goblin

Kuldotha Rebirth

As an additional cost to cast this spell, sacrifice an artifact.
Create three 1/1 red Goblin creature tokens.

Melt Terrain

Destroy target land. Melt Terrain deals 2 damage to that land's controller.

Molten Psyche

Each player shuffles the cards from their hand into their library, then draws that many cards.
Metalcraft — If you control three or more artifacts, Molten Psyche deals damage to each opponent equal to the number of cards that player has drawn this turn.

Ogre Geargrabber

Whenever this creature attacks, gain control of target Equipment an opponent controls until end of turn. Attach it to this creature. When you lose control of that Equipment, unattach it.

Scars of Mirrodin