Stony Strength

The untap clause splits this pump spell into two jobs that share a single green mana. The counter is permanent, so on a blocker it buys a body that survives the swing it just made and grows for the next one; that half is unremarkable. The wrinkle lives in the untap. Any creature you control that pays for its work by tapping (a mana dork, a creature that draws or pings on tap, an attacker mid-combat) gets to do that work a second time, and the +1/+1 counter becomes almost incidental to the activation you just refunded. That dual identity is why the card reads narrow and plays wide: because it happens at instant speed, one green source can pseudo-vigilance an attacker after blockers are declared, blank a tapper effect aimed at your dork, or squeeze another use out of an engine on the turn it is otherwise spent. The target restriction (a creature you control) is the boundary that keeps it a green trick rather than a colorless untapper, but within your own board the flexibility is real: the counter guarantees the spell is never a dead card, and the untap decides which of the two games you are actually playing that turn.