Voltaic Brawler

It ships with exactly two shots of ammunition. The energy it produces on entry funds two attacks as a 4/3 trampler, and once that tank is dry it lapses into a plain 3/2 unless something refills it. That arc is the entire design lever: unsupported, the creature pays its own way for the first couple of combats and then costs you nothing further; wired into a deck that keeps energy flowing, it never stops being an oversized trampler for a single counter each swing. This is what makes energy such a tidy resource for aggressive bodies. The creature carries its own fuel, and the deckbuilder's job becomes keeping the reservoir topped off rather than committing extra cards to pump it. The trample clause pulls more weight than the +1/+1: a 4/3 that gets through chump blockers is a genuine clock, and against a wall of ground defenders it keeps the damage arriving where a bigger vanilla beater would just stall. It gates a creature's ceiling by resource availability rather than the usual sorcery-speed limit or once-per-game cap, which is a cleaner way to build a Gruul beater whose upside scales with how hard you commit to the mechanic.