Signature card

A signature card is a card most associated with a Duelist, and tends to be used in a majority of their Duels. Duelists may have more than one signature card. Signature cards tend to be Monster Cards and to have alternate artworks in the OCG and TCG.

In Yu-Gi-Oh! 5D's, they tend to be Synchro Monsters; and in Yu-Gi-Oh! ZEXAL, they tend to be Xyz Monsters. Signature Monster Cards may also be called Ace Monsters.

Some video games have a similar concept known as a Key Card, in which the player selects a certain card as their "ace". Yu-Gi-Oh! The Duelists of the Roses has "Deck Leaders".