mtg card that changes all creature types I'll let you copy, but change it a bit Shapeshifters with changeling limited to

But probably the most obvious examples are the Plague Rat and Benalish Hero decks

Example Decklist: Rat Colony in Historic Brawl Rat Colony | Illustration by Suzanne Helmigh Commander (1) Creature (46) Rat Colony x44 Crashing Drawbridge Pack Rat Sorcery (5) Bloodchief's Thirst Echoing Return Reanimate Unearth Agadeem's Awakening Instant (4) Cut Down Dark Ritual Fatal Push Dismember Enchantment (3) Black Market Connections Phyrexian Arena Necropotence Artifact (3) Jet Medallion Bontu's Monument Herald's Horn Land (38) Bloodstained Mire Cavern of Souls Marsh Flats Mudflat Village Nykthos, Shrine to Nyx Phyrexian Tower Polluted Delta Susur Secundi, Void Altar Swamp x26 Swarmyard Urborg, Tomb of Yawgmoth Verdant Catacombs Witch's Cottage I wanted to showcase a deck you can build for relatively cheap on Arena

Even today, the idea of Skullclamp just screams card advantage, and it still shows up a lot in Commander where its allowed

But for a guy like me, being able to sell it is life-changing

Phyrexian Obliterator Phyrexian Obliterator limits the number of playable removal spells against it