If u beat the game in 5 hours or less, Elliot will begin the next game with all weapons that are availible to him in his inventory. Each weapon will also have unlimited ammo for your second trip. The ray gun will also be accessible too.
Complete the game on hard mode.
At the title screen, press the following:
x, y, a, r, start, l, start.
At the door that says staff only the 4-Digit code is 1224