Cheat: Free Rare Cards:
Enter the following names to receive the corresponding cards.
Tri-Horn Dragon Card: GOD OF CARDS
Cosmo Queen Card: KONAMI
Zera the Mant Card: XBOX

Cheat: Use Opponent's Decks:
Beat every opponent in triple duel mode and hold X at the opponent selection screen in single duel mode.

Hint: Alternate Backgrounds:
In the main menu highlight single or triple duel and press X. The background will change to an unlocked card.