Dross Scorpion

Whenever Dross Scorpion or another artifact creature dies, you may untap target artifact.

Marble Titan

Creatures with power 3 or greater don't untap during their controllers' untap steps.

Voltaic Construct

Mirran Spy

Flying
Whenever you cast an artifact spell, you may untap target creature.

Dr. Madison Li

Whenever you cast an artifact spell, you get {E} (an energy counter).
{T}, Pay {E}: Target creature gets +1/+0 and gains trample and haste until end of turn.
{T}, Pay {E}{E}{E}: Draw a card.
{T}, Pay {E}{E}{E}{E}{E}: Return target artifact card from your graveyard to the battlefield tapped.