Ninja Gaiden III: The Ancient Ship of Doom

Codes

• 99 Continues

  At the title screen, let it fade out to the intro and press Start to go back to the title screen again, repeat this 6 more times (you should have seen the title screen a total of 8 times), at the 8th title screen, press and hold Up, Left, A, B & Select and press Start. If done right, you'll have 99 continues.
  

• Full HP

  Japan version only
  

  Effect	Code
  Restore HP.	Press 'Up' + 'Start' during the game

Passwords

• Act Passwords (Japanese version)

  M - Medicine potion, P - Power-up, R - Ryu, S - Shuriken
  

  Effect	Password
  Act I	SRMP
  Act II	SMRS
  Act III	PSMR
  Act IV	MPSR
  Act V	RSMP
  Act VI	RRPM
  Act VII	MPRS

Glitches

Reappearing 1-up glitch

In Stage 6-2B, grab the 1-up, backtrack to 6-2A, then return to 6-2B. The 1-up will have reappeared, along with all other power-ups in the room. You can repeat this process until the timer runs out.
In Stage 7-2D, grab the 1-up, backtrack to 7-2C, then return to 7-2D. The 1-up will have reappeared, including all other power-ups in the room. Again, this can be done repeatedly until the timer runs out.