Get Progressive Scan Mode
If you have a progressive screen TV go to codes and enter 
RIGHT, UP, RIGHT, RIGHT, UP, RIGHT, RIGHT, RIGHT, UP, RIGHT.  

WARNING: If the screen turns blue you do not have a progressive scan TV and 
you will HAVE TO REBOOT THE PS2 to get it back to normal.

Level Select:
Enter Down, Left, Left, Down, Left, Down, Right, Down, Left, Down as a code. 
Hold R1 at the main menu to select level. 

Extra Special Features:
Enter Left, Down, Up, Left, Right, Up, Down, Left, Right, Down as a code. 

Extra Items:
Enter Right, Right, Right, Right, Right, Left, Left, Left, Up, Up as a code. 

Better Weapons:
Enter Right, Up, Down, Down, Up, Right, Right, Up, Down, Down as a code. 

Easy Mode:
Enter Up, Down, Down, Down, Down, Down, Down, Down, Down, Up as a code. 

Normal Mode:
Enter Up, Down, Up, Down, Up, Down, Up, Down, Up, Down as a code