Collector's Cage

Hideaway 5 (When this artifact enters, look at the top five cards of your library, exile one face down, then put the rest on the bottom in a random order.)
{1}, {T}: Put a +1/+1 counter on target creature you control. Then if you control three or more creatures with different powers, you may play the exiled card without paying its mana cost.

Ezrim, Agency Chief

Flying
When Ezrim, Agency Chief enters, investigate twice. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
{1}, Sacrifice an artifact: Ezrim gains your choice of vigilance, lifelink, or hexproof until end of turn.

Worldwalker Helm

If you would create one or more artifact tokens, instead create those tokens plus an additional Map token. (It's an artifact with "{1}, {T}, Sacrifice this artifact: Target creature you control explores. Activate only as a sorcery.")
{1}{U}, {T}: Create a token that's a copy of target artifact token you control.

Gandalf the White

Flash
You may cast legendary spells and artifact spells as though they had flash.
If a legendary permanent or an artifact entering or leaving the battlefield causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Vantress Visions

Copy target activated or triggered ability you control. You may choose new targets for the copy.

Virtue of Knowledge

If a permanent entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Virtue of Knowledge // Vantress Visions

Kappa Cannoneer

Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)
Ward {4}
Whenever Kappa Cannoneer or another artifact you control enters, put a +1/+1 counter on Kappa Cannoneer and it can't be blocked this turn.

Dreams of the Dead

{1}{U}: Return target white or black creature card from your graveyard to the battlefield. That creature gains "Cumulative upkeep {2}." If the creature would leave the battlefield, exile it instead of putting it anywhere else. (At the beginning of its controller's upkeep, that player puts an age counter on it, then sacrifices it unless they pay its upkeep cost for each age counter on it.)

Mirage Mirror

{2}: Mirage Mirror becomes a copy of target artifact, creature, enchantment, or land until end of turn.

Leonin Elder

Whenever an artifact enters, you may gain 1 life.

Glassdust Hulk

Whenever another artifact you control enters, Glassdust Hulk gets +1/+1 until end of turn and can't be blocked this turn.
Cycling {W/U} ({W/U}, Discard this card: Draw a card.)