During play, press the ~ key to open the console. Now enter one of the following codes and press Enter to activate.

ClayburnFallmont    Full Ammo
StanGable           Infinite Ammo
JeffersonDarcy      More Hit Points
AceEvans            Invisible
RogerPhillips       Artillery Strikes

Thanks to Revolution readers DALE9276, Scottwars, James, Ben Ramey, josh strickland, and doomboy536!