Level select:
Enter 8ODYS as a code. 

Invincibility:
Enter HPPYHPPY as a code. 

All weapons:
Enter RCKTSRDGLR as a code.

Campaign mode bonus level:
Enter WRDRB as a code to unlock the Boat Assault secret level after campaign 
mode is completed.

Brandon's gang:
Enter NNKNHCKS as a code. 

Custom 1 gang:
Enter TRDDYBRRKS as a code to unlock the Custom 1 gang (M2 Hydra tank ) in 
multi-player mode. 

Customized gangs:
When you enter TRDDYBRRKS code and Custom Gang appears at the bottom, you 
can actually type in letters and customize your own gangs. For example, if 
you enter TRDDYBRRKS and then enter X, you get grenades, two Goliath tanks, 
2 FLP-Es, and a Laser Tank. You can also type in various combinations to get 
various groups. For example, enter SGG for three Goliath tanks, an Inferno, 
and a Motortank. 

Suicide:
Press C-Up + C-Down + C-Left + C-Right during game play. This is especially 
useful if you have selected the wrong tank with the invincibility code 
activated. 

Multi-player weapons power-up:
Begin game play in multi-player mode and collect at least fifteen of one 
weapon, except for grenades. Aim at an opponent, then press A + B + Z to 
fire a powered-up version of that weapon. 

Press A + B at the same time to unleash powered-up versions of weapons in 
single player mode. In order to do this trick you must have fifteen of that 
type of weapon. Note: Press Z when guided missiles are under your control 
to fire a blue laser.