Savage Summoning

Three favors bundled into one mana, and the cleverest is the one that changes when you play, not whether your spell resolves. The uncounterable clause on the instant itself, and then on the creature it primes, is the obvious half: it walks your bomb past a wall of permission. But the flash grant is the part most players underrate, because it turns this into a tempo lever rather than pure protection. Hold this and a creature spell on your opponent's turn, fire Savage Summoning during their end step or in combat, and a threat you had no other moment to deploy lands after their sorcery-speed sweepers have missed, arriving as an uninvited blocker or an ambush attacker the following turn. The +1/+1 counter is the small sweetener that keeps the cast worthwhile even when no counterspell ever appears: you have spent a mana to make the next body a hair bigger and given it functional flash. What it resolves is green's historical helplessness against blue's stack control. Green has plenty of fat to jam but few ways in its own philosophy to insist a threat sticks; handing it a literal counterspell would be off-color. This answers the problem in green's terms instead, accelerating the creature into a moment blue's permission is spent and stapling an anti-counter shield to it on the way down. Instant-speed removal can still answer the body once it lands, but the specific line of defense this shuts off (counterspells) is the one green could never address on its own.