At Title Screen, press Left, Left, L Button, L Button,
Right, Right, Left, Left.
At Title Screen, press L button, L button, L button, C-Right,
Right, Left, Left, C-Left.
At Title Screen, press R Button, C-right, Right, L Button,
C-left, Left, C-right, Right.
Press the R Button 7 Times and Then Press Left on the
D-pad. You should hear a sound. Now go to the Cheat Menu and there it is
at the very top.
At title screen, press L button, C-Left, Left, R button,
C-Right, Right, Left, Left, Right You should hear a sound. There should
be a new option in the Cheat Menu.
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".
You will gradually regain your energy.
For Big Duke, you must have invincibility. Then...