Minsc & Boo, Timeless Heroes

The −2 is a genuinely nasty piece of Gruul design, but the card's real trick is that it grows its own ammunition. Boo, the recurring 1/1 Hamster with trample and haste, is not flavor dressing: he is a body the +1 wants to enlarge and the −2 wants to eat. Stack a few +1/+1 counters onto him, sacrifice him, and the walker hurls that power at any target while the Hamster clause refunds a fistful of cards, converting a single sacrifice into both a burn spell and a draw spell at once. Generate the token, grow it, cash it in for damage and cards: that loop is a closed engine most planeswalkers only gesture at across separate ability slots. The restraint comes from the timing. Every loyalty ability is sorcery-speed, so the payload accumulates over turns rather than being assembled in a single window, and Boo returns only on your upkeep, one body per turn cycle. The +1 also reaches past Boo to any creature with trample or haste, rewarding a board that already trades in evasion and speed instead of fixating on a single target. Its ability to helm a deck follows directly from the engine: a commander that manufactures its own sacrifice fodder and pays you for eating it wants to be built around, and the Hamster-draw rider means Boo specifically is worth protecting and reloading, not just whatever creature happens to be lying around.