Second Wind

The trick lives in the tap symbol being the cost, not the effect, and in the abilities belonging to the Aura rather than the creature it sits on. Second Wind itself taps to tap or untap whatever it enchants, which means the enchanted creature is never the one spending the activation. That separation is the whole design: because the Aura pays its own way, the creature stays free to do what it does, and the untap half hands it a second use without asking it to stay home. Send a creature into combat (declaring it as an attacker taps it), then untap it with the Aura so it can block on the swing back; or untap a creature with a tap ability worth firing twice, turning one activation into two. The catch is that Second Wind can only fire one of its two abilities per turn, since both share the same tapped state, so it is one extra tap-or-untap per cycle, not a free vigilance engine. It reads as a quiet permission slip rather than a payoff: the value comes from the body underneath, and the Aura just gives that body a second window. Where most pseudo-vigilance arrives as a granted keyword, this does the same job through a repeatable, externally-paid activation, which is why it scales with any creature whose tap is worth doubling rather than with the keyword itself. Low-rarity tinkering of exactly the kind that rewards finding the right host.