Fountain of Youth- Shoot or blow up a water fountain, fire hydrant, or even a toilet. Then walk over to the water that's squirting up and hold A (default). You will gradually regain your energy.
Cheat Menu- Press the following at the main menu to access the hidden cheat menu: Left, Left, L, L, Right, Right, Left, Left. Now the cheat menu will be accessible.
Turn Items On- Enter the code for the cheat menu. Now at the main menu imput R, Right C, Right, L, Left C, Left, Right C, Right. This will enable all items to be toggled on or off.