Start the game with a command-line parameter "-console" (ie, Solomissions.exe -console). After that, during gameplay, press ~ ( tilde ) to bring down the console and type any of the following cheat codes:

Cheat Code - Granted Wish

god - God Mode
noclip - No Clipping Mode
fly - Fly Mode
map X# - Skip to Map # (1-6)
timescale # - Set Game Speed to # (normal is 1)
endgame - Win Game
notarget - Enemies No Longer Shoot