Madness Interactive Cheats

Enable the minnie code. Then, go to "Experiment",
get a flamethrower, and start shooting it in any direction. While
you are still shooting, press [Enter] to go back to the
main menu. Then, go back to "Experiment" (with the minnie
still enabled) and shoot your "minnie" gun. The ammo
bar (flamethrower ammunition) at the top right of the screen goes
down, and goes past the little box it is in. It will continue
to go down and off screen as long as you hold the Left Mouse
Button. [Screenshot]
Map: Weapons on keyboard

Enter at the cheat menu