Inspirit

Two effects bundled into one instant, and the untap clause is the half that does the real work. A vigilance-grant in disguise: cast it after declaring an attacker and the creature swings while staying back to block, or cast it on an opponent's turn to wake a tapped blocker for an ambush. The +2/+4 wins the combat math, but the toughness skew toward defense tells you what the card was built for: keeping a creature alive through a block rather than pushing extra damage through. The untap also matters when an opponent attacks into a tapped-down creature, hoping to land a hit while it cannot block; the surprise refresh turns a clean swing into a trade. The catch is that you have to hold three mana open and read combat correctly, because a misjudged trick costs you a turn of tempo for nothing. It belongs to the long tradition of white tricks that turn a fair fight into an unfair one by manipulating who is tapped and when, the kind of effect that punishes an opponent for committing to an attack or a block before the trick can answer it.