Rubblebelt Braggart

In Commander, Rubblebelt Braggart does its best work in decks that reliably have one massive creature on board — think Voltron shells or stompy lists where copying the biggest threat doubles your pressure immediately. Outside Commander, the four-mana cost is a liability in faster formats: Modern and Pioneer have Clone variants that offer more flexibility or cost less, and Rubblebelt Braggart's condition of copying only your largest creature is too narrow to compete with premium shapeshifter options. In Standard and Pauper it's a legitimate roleplayer where creature-copy effects are thinner on the ground, and any deck that consistently lands a dominant beater by turn three or four will get real value from it.