Goblin War Buggy

Echo was the mechanic that tried to make haste honest: you get the burst now, you pay for it later. The buggy is that bargain rendered in the simplest possible terms. It arrives swinging as a fully realized attacker thanks to haste, no summoning sickness, no setup. Then the bill comes due exactly once, at your next upkeep, when you either pay or watch it drive off. The accounting is what makes it elegant: the echo cost is identical to the casting cost, so you are paying for the creature twice with one free attack slotted in between. That front-loaded swing is the entire pitch. You are renting a 2/2 for a single hasty hit, and keeping it past the first upkeep means covering its full price a second time. After that payment clears, it is just a 2/2 that already got its damage in early. The flavor lands the joke, too: a goblin contraption that screams onto the battlefield, does its damage, and demands a second deposit before it will stick around. Echo never quite held its place as a mechanic (the accounting friction and the feel-bad of sacrificing your own creature pushed it out of rotation), but the buggy is a tidy specimen of what it was for: front-loading tempo and back-loading the cost, so the rate reads aggressive when it lands and sober at the upkeep after.