D2 Codes -

Control logo:
Press the Analog-stick or D-pad at the title screen to rotate the game's logo.

Millennium countdown:
Successfully complete the game and allow the credits to end. Press A to display a black screen with a countdown to the year 2000. Note: The countdown still progresses even after the year 2000 has passed.

Unlimited grenades, shotgun shells, and first aid sprays:
When you leave the last cabin on Disc 4 you will find two grenades, shotgun shells, and various first aid sprays in the snow. Pick these up, then re-enter the cabin. Go back outside and all the items will be there again. Note: This also works by saving than restarting your file in any place on the last path.