Urza's Engine

A Juggernaut that pays mana to band is one of the stranger artifact designs of its era, and it makes more sense once you read banding as a damage-assignment trick rather than an evasion keyword. The first activation buys banding for itself, which on defense lets you, the blocker's controller, decide how the attacker's damage is split across the band; on offense, a band of attackers is blocked as a group and you control how the blocker's damage lands. The second activation hands trample to the rest of the band, so a wall of small attackers funnels excess damage through to the face. Stacked together, the two abilities turn a 1/5 body into the anchor of a combat-math engine: the trample on the Engine itself, the lent trample on its bandmates, and your control over how a blocker's damage is distributed combine into a way to attack into a board you would normally lose the math against. The catch is that banding is one of the most opaque rules sets the game ever shipped, and the activations cost three mana apiece, so the payoff demands both a board to band with and a clear head about who is assigning what. It belongs to a brief window when artifacts were given keyword-soup utility rather than clean rates, and it reads today as a relic of how much combat complexity early design was willing to fold into a single creature.