Brass Squire
Mirrodin Besieged — uncommon
Artifact Creature — Myr
Brass Squire rulings:
2011-06-01: If one of the targets is illegal when the activated ability resolves, nothing will happen and the Equipment won't move. Notably, if an opponent gains control of either target in response, the Equipment won't move.
2011-06-01: Unlike the equip ability, Brass Squire's ability can be activated whenever you could cast an instant.