Yu-Gi-Oh! Duel Monsters Expert 3 Cheats

Certain duelists have extra requirements to unlock. You must constantly meet these requirements, or they will vanish from the selection screen. If you defeat a duelist with special requirements ten times, they will be permanently selectable, regardless of their past requirements. For example, if you beat Jounouchi ten times, you can then duel him even if you have a Jinzo card in your deck. Losses and ties don't count against your total wins.

When choosing a duelist, hold down L until the duel starts. The gameplay speed will be twice as fast.