Goblin Goliath

Built for the kitchen table and honest about it: the enters-the-battlefield trigger scales to your opponent count, which means it does almost nothing in a duel and blossoms in a four-player pod. That opponent-counting clause is the tell that this was designed for multiplayer first, a Goblin meant to walk onto a crowded board and immediately hand you a small army. The activated ability is where the real payoff lives. For ten mana total across the cast and the first activation, you turn every source you control into a doubler against your opponents: combat damage, burn, ping effects, all of it lands twice. Point it at the Goblin swarm the front half just made and you have a one-card damage-multiplication engine, though the this-turn-only window (it only applies to damage dealt this turn, and it takes a tap to arm) keeps it from becoming a permanent fixture. This replacement effect formalizes an effect red has flirted with for years, from Furnace of Rath to Gratuitous Violence, but this version is one-sided rather than a symmetric enchantment, which is exactly what a casual red deck wants: your damage doubled, theirs untouched, aimed wherever the table is weakest.