Merfolk Skyscout

The untap trigger here is the whole engine, and it fires on both attack and block, which means the card keeps working whether it is the aggressor or the defender. Most untap effects in blue are one-shots welded to a spell; stapling one to a flying body that goes off every combat turns it into a repeatable resource loop instead of a single burst. The obvious payoff is your own mana: send it in, untap a land or a mana rock, and you have effectively cast a flyer that refunds part of its cost every time it commits to combat. The trigger keys off the declaration of an attack or block, not on connecting, so a chump-blocked or fully blocked-out flyer still untaps its target. The any-permanent clause opens stranger lines: reset one of your tapped creatures to hold the fort, re-enable a tap-ability on an artifact or another creature, or re-arm anything you have already spent this turn. What keeps the engine honest is that it is married to combat. You cannot fire it at instant speed off-combat, and you have to send a fragile body into an attack or a block to collect, so the loop is only as good as your willingness to expose it. It is a build-around in the truest sense: harmless as a beater, quietly powerful once you own a tap-ability worth springing every turn.