Contra

Developed by >Konami
Genre: Action Players: 1-2

30 Lives
At the title screen, press Up, Up, Down, Down, Left, Right, Left, Right, B, A. To finish the code, press Start for a one-player game or Select, Start for two players.

Game Genie Codes
from Anthony Greco (AntMG1@ibm.net) 
SLAIUZ  Infinite lives  
GXIIUX  Keep weapons after death    
SLTIYG  Invincibility   
PEIIXZ  Start new life with machine gun 
ZEIIXZ  Start new life with flame thrower   
LEIIXZ  Start new life with spread gun  
GEIIXZ  Start new life wih laser    
SXZGEK  Weird color code

Harder Game
from Nemesis940@AOL.COM
For a greater challenge, beat the game then immediately start over. You'll start from the beginning with whatever lives you had left and changes to the game have been made (e.g. more enemies, they shoot at you more, enemies placed differently.) You can repeat this process as many times you want until you die or quit.

Steal Lives
from istanbul@airmail.net
If you're playing a two-player game and you die, hit A and B simultaneously to steal one of player two's lives.

Contra Force

Developed by Konami
Genre: Action Players: 1-2

30 Lives
from Reese Romney (r_romney@hotmail.com)
When Contra Force is scrolling down the screen after game is turned on, quickly press Up, Up, Down, Down, Left, Right, Left, Right, A, B and Select, Start for a one player game or Select, Select, Start for a two player game.

Continue
from thoo@mother.com
At the game over screen, Hold A + B + Select and press Start. If you did it right you'll resume play where you died.

Game Genie Codes
from Jason Washington 
AANVIAPA  Infinite lives-all characters
PAUYTTLE  Start all characters with 9 lives