Ornithopter

Free to cast, and that single fact has carried it through three decades of combo and artifact-aggro design. The zero-mana cost makes it a metalcraft enabler, an affinity discount, a sacrifice target for Arcbound Ravager, and a body to wear equipment, all at once, while flying gives it the one piece of evasion that lets a 0-power creature still threaten damage once it picks up a sword. The 0/2 body matters more than the empty power suggests: that second point of toughness shrugs off the incidental one-damage pings that delete a Memnite, so it sticks around long enough to discount multiple affinity spells or hold a Cranial Plating rather than dying before it earns its keep. Every artifact-aggro shell in the game's history has run it, every Tinker deck in eternal formats has eyed it as fodder, and the more recent vehicle sets had to be costed against the assumption that a free flying body already exists. The card sits at a load-bearing point on the cost curve: zero-mana creatures with evasion are design space Wizards almost never reopens, because the downstream interactions (free attackers, free equip targets, free sacrifice fuel) compound in ways no single printing can anticipate. The rate has not been meaningfully matched since.