Safe Passage
During Level 1, hit B and Right repeatedly. You won't gather
weapons or power-ups, but you'll jump through this first level
relatively unharmed.
Six Credits
At the title screen, highlight Option. Press and hold R, L, Up,
and Start. Begin the game. When you die, your credits will have
increased to six at the screen that asks if you want to continue.
Napalm Gun:
Start a game, and on the first stage, go to the boss without shooting
any enemies. When you get to the end of the stage, just shoot the boss
do not hit the side guns. When the boss is destroyed, and you start
the next mission, cycle through your weapons. There is a new one, "Napalm."