Revengeance mode
On the title screen, enter the Konami code (Up, Up, Down, Down, Left, Right, Left, Right, Circle, X). Revengeance mode will be made available as a difficulty setting.
Unlimited Item Stocking
If you collect all items from boxes in an area, press (Select) and enter (Customization). Once you exit the customization screen, all item boxes will be reset, allowing you to fully stock up on items. Repeat as many times you wish.