Quicksand

A colorless mana source that doubles as a combat trap, and the design discipline that makes it tick is the sacrifice clause: this is not repeatable removal, it is a single ambush priced into a land slot you were going to play anyway. The strict targeting (an attacking creature without flying) is the constraint that keeps the rate honest. It cannot be aimed at blockers, cannot touch anything on the ground that stays home, and cannot stop fliers at all, so the card rewards the defending player for letting an attack commit before springing the trap. The -1/-2 split is the tell of its era's design priorities: just enough toughness reduction to kill the small aggressive creatures of the day, just enough power reduction to blunt a swing, but never a clean answer to a real threat. What it represents is the colorless utility land as a deckbuilding tax loophole: a way for any color to buy interaction without spending a spell or a colored source, paid for entirely in the opportunity cost of a land that taps for colorless mana. That idea (the land that quietly does a spell's worth of work the turn you need it) has been a recurring lever in Magic's design ever since, and Quicksand is one of its cleaner early statements.