Wall of Blood

The activation has no "once" in it: each life payment is a separate pump, so a single 0/2 can swell to whatever your life total allows, all at once, and all for free in mana. That turns a defenseless body into a delivery system. Hand it to Fling, the canonical partner, and the inflated Wall stops being a blocker and becomes the whole combo, hurled at a face for lethal in a single burst. The defender clause is half the joke: it can never attack, so the only honest way to cash in all that toughness is to throw it somewhere. The other half is the resource. Life is the cheapest currency black and red trade in, and a deck built to win in one explosion rarely cares about its life total once the chain starts. The cleverness is in how an uncapped pump was made fair: stranding the result on a creature that cannot connect forced the payoff to live elsewhere, which is exactly what makes the Wall a component rather than a finisher on its own. It reads like a defensive common right up until you notice the cost has no ceiling, at which point it stops being a wall and becomes ammunition.