Secret Date
First, 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.
Shower Scene
Finish game in Normal Mode, then start a new game in Hard Mode. When you get to Laura's room, press A to see Laura's shower scene.
Zero Enemies
In Laura's room enter: a, l, c, x and there will be no enemies.