If you want to earn 30,000 bonus points, make sure you end a level with eleven times more shurikens than the number of lives you have left.
Extra Lives
One the second stage of level four,fire at the base of the first conveyer belt.A special Musashi symbol will appear.Hop onto the conveyor belt and let it carry you to the end.You lose a life but you gain 2.Keep doing this until you have as many lives as you want/need.
Mystic Shield
When you have the Weapons Upgrade item, walk and you'll notice the shinobi holding a light on his wrist. This light is the Mystic Shield. It will protect you against small projectiles like ninja stars and bullets, but not against bigger ones like the grenades the soldiers throw. Note: The shield is only activated when you walk.
Stage Practice Mode
Hold down the A, B and C buttons, and press START at the Opening Screen.
Unlimited Knives
At The very beginning of the game go to the options menu and change the number of weapons to 00, then do not do anything for ten seconds, then the 00 will become an infinity sign and your weapons will never run out.
30,000 Bonus Points...