Rampage: Total Destruction Cheats for GameCube

Hold R and L at the main Menu screen then type the following codes
141421 - Unlock All Monsters
000000 - Deactivates all active codes
986960 - Invincible to all Military Attacks(Bombers,Infintry,Tanks,etc.)
071767 - One hit Destruction(Buildings only)
667300 - View Opening Theme
667301 - View Ending Theme
667302 - View Credits

Unlock Special Monsters
Complete the Special Star Challenges in the cities to unlock the corresponding monster.
Unlock Eyegore:
Complete ALL the Challenge Stars in ALL the cities

Unlock Philbert:
Complete ALL the Par Point Stars in ALL the cities
Unlock Bubba:
Unlock ALL the secret monsters including Philbert and Eyegore.

Unlockable Monsters
The following mosters in the cities listed below are used to unlock the other monsters. It is poosible that there may be more then one monster to unlock the secret ones. And you might have to re-do the city to unlock the other ones that are in it.
Unlock Amanda:
Play as Kyle in Los Angeles
Unlock Bart:
Play as Kingston in Los Angeles

Unlock Cal:
Play as Kyle in Los Angeles

Unlock Croc:
Play as Rojo in Hong Kong

Unlock Edwin:
Play as Wally in London

Unlock Harry:
Play as Marco in Chicago

Unlock Icky:
Play as Ralph in London
Unlock Jack:
Play as Harry in Las Vegas

Unlock Jill:
Play as Amanda in Hong Kong
Unlock Joe:
Play as Natalie in New York

Unlock Kingston:
Play as Lizzie in Las Vegas

Unlock Kyle:
Play as Kingston in London
Unlock Leon:
Play as any starting monster in Las Vegas

Unlock Marco:
Play as Ralph in San Francisco

Unlock Natalie:
Play as Marco in San Francisco

Unlock Nick:
Play as Harry in Chicago
Unlock Rocky:
Play as Cal in New York
Unlock Rojo:
Play as Kyle in Chicago
Unlock Shelby:
Play as Lizzie in San Francisco
Unlock Venus:
Play as Croc in Hong Kong

Unlock Wally:
Play as Marco in New York