The Last Ninja 1

Not enough lives?  Well, save your game and enter your 
hexstyle editor with that saved game file open for editing. 
Change the byte at offset 59(hex) to FF. The FF will give 
you 255 lives.  
The bottom status screen will be cluttered with "lives", but 
they won't affect the game.

Also, try this cheat for infinite lives - type the 
following from the DOS prompt:

For the CGA version of this game, type:
ren c.exe cheater.cht
debug cheater.cht
e 9b50 90 90 90 90
Then type: w
           q

For the EGA version of this game, type:
ren e.exe cheater.cht
debug cheater.cht
e 9f16 90 90 90 90
Then type: w
           q

Then rename CHEATER.CHT back to its previous name.