Heavy Arbalest

The trade-off is the whole engine: equip this and the creature stops untapping, which means the ping costs you a permanent commitment, not a free tap each turn. That clause turns a creature into a stationary turret. Once it fires it stays tapped, so it can no longer attack or block, no longer feed any other tap ability, because it sits tapped the moment it fires. In exchange you get a repeatable two-damage shot at any target, machine-gun removal that grinds down small creatures, planeswalkers, or faces across a long game. Everything hinges on the body underneath it. A vanilla beater becomes a worse beater that pings; a creature with its own untap effect (Aphetto Alchemist, or anything that ignores the untap restriction outright) sidesteps the downside entirely and turns the equipment into a damage faucet limited only by mana. As artifact removal-on-a-stick, it asks the deckbuilder to solve the untap problem first and reap the rewards second, a sharper puzzle than the rate suggests. Without that solution it is a slow, expensive way to deal two; with it, it is a recurring threat that demands an answer.