The Rename Card allows the player to rename a character. It is a reward at the Coliseum after betting an Elixir and defeating the Cactuar. The Rename Card can further be bet for the Miracle Shoes, if the player can beat the Fiend Dragon.
The Rename Card allows the player to rename a GF. Another item, Pet Nametag, allows the player to rename Angelo. Rename Cards can be modified from a Catoblepas card, one can be acquired from Zone for giving him The Girl Next Door magazine on the White SeeD Ship, and it's one of the rewards the player can acquire by challenging other inmates in a card game in D-District Prison.
The Pet Nametag can be found in D-District Prison Floor 2. Another one is given by a man outside the Timber Maniacs building in Timber. The player must return to Timber after leaving it the first time, and encourage the man. Later, he will give the party the Pet Nametag item.
Called the Namingway Card and featuring a picture of the Hummingway Namingway from Final Fantasy IV, the player can show it to a man in Daguerreo and he will allow they player to rename a character. Namingway in the original Final Fantasy IV could change a character's name.
The card can also be used to play Tetra Master, though the player would run the risk of losing it, as there are only two in the entire game. One is in Kuja's room in the Desert Palace (near the teleporter, only after Eiko has been kidnapped). The other is in Treno, during the card tournament.
When the player is in control of Vivi, they are given the option of "going home", or staying in Treno. Choosing the latter will give Zidane a different opponent in the card tournament's second round, who holds the Namingway card.
The Rename Card allows the player to rename an aeon. It can be dropped by Espada, stolen from Ornitholestes, bribed from Zaurus and won by having a top scorer in the tournament and league modes of Blitzball.