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.

Prosperous Pirates

When Prosperous Pirates enters, create two Treasure tokens. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Efficient Construction

Whenever you cast an artifact spell, create a 1/1 colorless Thopter artifact creature token with flying.

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}.

Floodhound

{3}, {T}: Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Press for Answers

Tap target creature. It doesn't untap during its controller's next untap step.
Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Salivating Gremlins

Whenever an artifact you control enters, Salivating Gremlins gets +2/+0 and gains trample until end of turn.

Moonsnare Prototype

{T}, Tap an untapped artifact or creature you control: Add {C}.
Channel — {4}{U}, Discard Moonsnare Prototype: The owner of target nonland permanent puts it on their choice of the top or bottom of their library.

Vedalken Certarch

Metalcraft — {T}: Tap target artifact, creature, or land. Activate only if you control three or more artifacts.

Welding Sparks

Welding Sparks deals X damage to target creature, where X is 3 plus the number of artifacts you control.

Scholar of Stars

When Scholar of Stars enters, if you control an artifact, draw a card.

Jace's Scrutiny

Target creature gets -4/-0 until end of turn.
Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Hold for Questioning

Enchant creature or planeswalker
When Hold for Questioning enters, tap enchanted permanent and investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
Enchanted permanent doesn't untap during its controller's untap step and its activated abilities can't be activated.

Bastion Inventor

Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Artificer's Epiphany

Draw two cards. If you control no artifacts, discard a card.

Wind-Kin Raiders

Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Flying