That honor is held by the Worlds Smallest Magic: The Gathering Exclusive Collector Set pictured above - a painfully adorable, now sadly discontinued joke product that included two itsy-bitsy duel decks composed of downsized, 1.2 x 1.8 inch cards, as well as teeny weeny spindown dice
There are many other card types other than Creatures, including but not limited to Enchantments , Artifacts , and Planeswalkers
As a great final touch, these croak counters remain on exiled cards even if an opponent removes Grolnok, meaning they can still be cast once Grolnok is replayed from the command zone later
In May 2021, a Pristine 10 graded version by BGS (Beckett Grading Services) was sold for a whopping $144,300, underscoring its value
Whereever you're buying these, just note the value may continue to rise, or crash unexpectedly