No enemies:
Press A, L, C, X while in Laura's room.

Secret date:
Set the Saturn's internal date to January 1. Your battery-saver will be set to 99 instead of 64. George's gun will be charged when it is found, and will now hold three shots.

Christmas message:
Set the Saturn's internal date to December 25. A hidden message will be displayed as the game loads.

Hidden scene:
Complete the game at the normal difficulty level and start a new game under the hard difficulty level. Press A when reaching Laura's room to view a shower scene.