Frogmite

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

Tormod's Crypt

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

Thought Monitor

Affinity for artifacts
Flying
When Thought Monitor enters the battlefield, draw two cards.

Pithing Needle

As Pithing Needle enters the battlefield, choose a card name.
Activated abilities of sources with the chosen name can't be activated unless they're mana abilities.

Ornithopter

Krark-Clan Ironworks

Shadowspear

Equipped creature gets +1/+1 and has trample and lifelink.
{1}: Permanents your opponents control lose hexproof and indestructible until end of turn.
Equip {2}

Mox Opal

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

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}.

Nettlecyst

Living weapon (When this Equipment enters the battlefield, create a 0/0 black Phyrexian Germ creature token, then attach this to it.)
Equipped creature gets +1/+1 for each artifact and/or enchantment you control.
Equip {2}

Inventors' Fair

At the beginning of your upkeep, if you control three or more artifacts, you gain 1 life.
{T}: Add {C}.
{4}, {T}, Sacrifice Inventors' Fair: Search your library for an artifact card, reveal it, put it into your hand, then shuffle. Activate only if you control three or more artifacts.

Seat of the Synod

Paradise Mantle

Equipped creature has "{T}: Add one mana of any color."
Equip {1}

Thoughtcast

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

Welding Jar

Sacrifice Welding Jar: Regenerate target artifact.

Cranial Plating

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

Springleaf Drum

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

Memnite

Darksteel Citadel

Patchwork Automaton

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
Whenever you cast an artifact spell, put a +1/+1 counter on Patchwork Automaton.