New Costumes and DX Camera
Legend of Zelda: The Wind Waker
Beat the game to unlock a couple new costumes.
Link will be dressed in his blue outfit throughout the adventure.
Link's sister will wear a skull shirt.
You will also have instant access to the DX Color Camera (even if you finished the game with the standard camera only).
Finally, all Hylian text will be translated into English the second time through.
To make this work, make sure you save at the end of the game, and start the game again with that save file.