Codes
To access the cheat menu, press and hold (in this order) L, B, then R. Then release B, then R, then L. Then enter specific code for the effect that you want. 

760611 11 Coninutes in Adventure Mode 
756287 All buildings and Objects become throwable 
112122 All buildings become in destructible 
316022 All monsters are invisible 
505634 All players are damage-proof 
174204 All Players are micro monsters 
817683 All players deal quad damage 
567980 Black & White Mode 
097401 Display version of game and time of completion in the Options 
492877 Health regenerates 
413403 No energy power-ups 
841720 No freeze tanks 
562142 No health power-ups 
134615 No Mothra power-ups 
119702 No rage power-ups 
443253 No Status HUD 
650867 One time energy (Energy doesn't recharge over time, but energy weapons do more damage) 
649640 P1 Always in Rage 
511012 P1 deals quad (4x) damage 
843901 P1 is damage-proof 
986875 P1 is micro monster (1/3 norm. size) 
122224 P2 Always in Rage 
815480 P2 deals quad damage 
706149 P2 is damage-proof 
971934 P2 is micro monster 
548053 P3 Always in Rage 
212454 P3 deals quad damage 
188522 P3 is damage-proof 
895636 P3 is micro monster 
451242 P4 Always in Rage 
286552 P4 deals quad damage 
286552 P4 is damage-proof 
795735 P4 is micro monster 
135984 Player Indicators always On 
913963 Smog Mode 
308929 Stronger Military 
677251 Super Energy (Constant Full energy ball) P1 
435976 Super Energy P2 
603696 Super Energy P3 
291680 Super Energy P4 
661334 Technicolor mode 
256806 Turn Military On/Off 
480148 Unlock all cities 
696924 Unlock all monsters except Orga 
537084 Unlock Destoroyah 
616233 Unlock Gigan 
225133 Unlock Godzilla 2K 
877467 Unlock King Ghidorah 
131008 Unlock Mecha Godzilla 
557456 Unlock Mecha King Ghidorah 
104332 Unlock Rodan 
202412 Unlocks Orga 
176542 View Credits