War-Torch Goblin

The threat does its work before combat damage even resolves: this is a deterrent dressed as a creature. The damage fires only at blocking creatures, which is its defining wrinkle. The goblin cannot snipe an untapped blocker on your turn or pick off an attacker; the moment something commits to combat, though, it becomes a legal target (any creature blocking on the opponent's behalf counts, whether it is stopping an attack on the player or guarding a planeswalker). Send it into the red zone and the defender faces a choice with no clean answer. Block, and the goblin trades itself to deal 2 to whatever stopped it, often enough to come out ahead; let it through, and the 1/1 chips in for one. That fork carries the design, and it sits in a long line of red one-drops built to make blocking math miserable rather than to win races outright. Sacrificing the body is what stops the effect from being free: the 2 damage costs you a card and another red mana to remove a blocker that was already committed. It rewards going wide, where one body spent to clear a key defender opens a lane for the rest. Modest by any rate, but precise about its job: a small piece of pressure that converts an opponent's defensive decision into a losing one.