Full life:
Hold II when using a potion after dying.

Be Hu Man at start of game:
Enter NODEGOSOOOOOOO as a password. Note: Enter MODE FOR OOOO OOO in Japanese version of the game.

Disable door noise:
Enter RMAYTJEOPHALUP as a password. Note: Enter PLAY THE ONGA KUN in Japanese version of the game.

Super password:
Enter 3WSURYXZY763TE to start with advanced items and abilities.

Hint: Secret weapons store:
Enter the house with a well in the first village. Fall down the well, and turn left towards the exit door. Place your character on that door, jump directly up, then hold Up while in mid-air. Enter the hidden door that appears above the exit door.