Personally I never played a "cheats game" online, but these do come in handy when you know the computer is  getting the upper hand.
                                                  
Type from enter key                                       Effect                  


POLO                                                            Remove Shadow
MARCO                                                        Reveal Map        
ROCK ON                                                    1000 Stone         
LUMBERJACK                                             1000 Wood        
ROBIN HOOD                                              1000 Gold          
CHEESE STEAK JIMMY'S                          1000 Food          
RESIGN                                                         Defeat yourself    
WIMPYWIMPYWIMPY                               Destroy yourself  
NATURAL WONDERS                                Control Nature    
HOW DO YOU TURN THIS ON                 Gives a 'cobra' car
TORPEDOx (Kills)                                         Opponent x  (x = opponent #)
TO SMITHEREENS                                      Gives a saboteur
BLACK DEATH                                            Destroying all the enemies
I LOVE THE MONKEY HEAD                    Gives a VDML
AEGIS                                                            Instant Building