Affa Guard Hound

Flash is the whole reason this combat trick wears a body. A pure +0/+3 instant has always been one of the most awkward effects in white's kit: cast it ahead of damage and you tip your hand, hold it and it sits dead in your grip if combat never comes. Stapling that toughness boost to a 2/2 with flash solves the dead-card problem by making the floor a creature. Leave the mana up, and if the opponent attacks or shoves a removal spell at one of your blockers, you flash this in, ambush-block or save the target, and keep a 2/2 on the board afterward. If nothing happens, you still got a creature for your three mana, just on a turn of your choosing. The +0/+3 itself is a defensive number, not an offensive one: it does not push extra damage through, it absorbs it, turning a profitable attack into a bad trade or letting a fragile creature survive a burn spell. The design is a tidy answer to a recurring tension in trick-style cards, which is that the worst outcome is paying for an effect you never get to use. Bundling the effect onto a permanent removes that downside entirely; the trick becomes a hedge that always cashes out as a creature.