What is the world's rarest yu gi oh card?

Answer 1

The second rarest card is split between several, they are the Worlds first and second place prizecards. They are,

Ulevo,

King of Destruction - Xexex,

Testament of the Arcane Lords,

Chimaera the Master of Beasts,

Tyr, the Vanquishing Warlord,

Aggiba, the Malevolent Sh'nn S'yo.

Only two cards exist of each of the above, though Testament, Chimaera and Tyr received super-rare reprints at the following year's participation card.
obelisk the tormenter