Command And Conquer 64 

Cheat mode 
At the "Press Start:
screen, press B, A, R(2), A, C-Right, Up, Down, A.
If you entered the code correctly, you will hear a sound.
Select the "Replay Mission" option at the main menu, then press L to display all missions and R to select your team.
During a mission, press L + R to display programming debug information.
Press L + R + Up to automatically win or L + R + Down to automatically lose.

Adjust battle screen 
At the battle screen:
hold L and press C-Up or C-Down to magnify and reduce the screen.

Easier building 
Highlight a unit that will be created from the toolbar:
then press A. Hold Z and press A after receiving the "Unit Ready" or "Construction Complete" message to 
build the same unit again without returning to the toolbar.