The most expensive Yu-Gi-Oh! card is 'Tyler the Great Warrior,' a one-of-a-kind card created for a Make-A-Wish request, which sold for over $300,000. Other highly valuable cards include the Alternate Artwork Gemini Elf T3-04, valued around $254,791, and the Masahiro the Dark Clown Japanese Tournament Prize card, which sold for approximately $173,923.