The Legend Of Zelda: Majora's Mask Codes -

 

Advance time:
Play the following notes on the Ocarina: (x2), (x2), (x2) travel to the next time it will be 6:00. . For example, if it is currently 6:00 PM on the First Day and you play the song, you will go to 6:00 AM on the Second Day (twelve hours forward). But, if you play the song at 4:00 AM on the First Day, you will go to 6:00 PM on the First Day (2 hours forward).

Slower time with normal movement rate:
Play the following notes on the Ocarina (The Song Of Time backwards): , , , , , . Play the song again to return to normal.

Heal signs:
Destroy a sign, then play the following notes on the Ocarina (The Song Of Healing): , , .

Alternate opening sequence:
Turn on the Nintendo 64. Quickly press and get to the main menu. At the main menu, press to get to the "Options" selection, then press . Once the options screen appears, press immediately. Do not move or change anything. Once at the main menu again, press to go back to the opening and watch the sequence, which should now be different.