At the New Game screen, hold the trigger buttons and press left, up, down, x, right, triangle, start. An input menu should appear. To enter more cheats at this screen, you have to do this again after entering one. Here they are:

SPACEFOLD: Gunpod power refreshes faster
MARSBASE: Missiles will reload faster
MIRIYA: Both reload faster
BACKSTABBER: Enemies explode after one shot from your guns; missiles do regular damage
SNIPER: One-shot kills in sniper mode
MISSMACROSS: Unlocks all paint schemes
WEWILLWIN: Unlocks all levels
WHERESMAX: Unlocks all Veritech models and earns every medal
SUPERMECH: Invincibility
MULTIMAYHEM: Unlocks all multiplayer levels
FLIPSIDE (PS2 Only): Flips the entire game upside down.

There is a way to disable the cheat codes. Just activate the menu and enter CLEAR. This will deactivate any codes you inputted.

Enter fighter training, and destroy the first two targets during weapons training. Then, Exit Training mode and enter Story Mode.

If your both running low on health have no fear. Change to Fighter mode (D-pad right) and boost (X) straight into a building or something.

You die and come back with full health, and this does not count as a point for him/her. He/She did not kill you.

Meritorious Service Medal: Unlock ''Izzy'' Paint Design

Distinguished Service Medal: Unlock ''Rick'' Paint Design

Master Airman Medal: Unlocks Nothing

RDF Flying Ace Medal: Unlocks ''Max'' Paint Design and ''Debris Field'' Versus Map (this medal is acheived by getting 3 ''Master Airman Medals'')

RDF Starburst Medal: Unlocks ''Flood City'' Versus Map

Titanium Medal of Valor Medal: Unlocks ''VF-1J''

Bronze Cross Medal: Unlocks Nothing

Silver Cross Medal: Unlocks Nothing (Acheive by getting 3 ''Bronze Cross Medals'' and killing 75 Battle Pods)

Gold Cross Medal: Unlocks Nothing (Acheive by getting 3 ''Silver Cross Medals'' and killing 100 Battle Pods)

Southern Cross Medal: Unlocks ''Armored Varitech'' and ''Factory'' Versus Map (Acheive by getting 3 ''Gold Cross Medals'')

Silver Shield Medal: Unlocks ''Miriya'' Paint Design and ''Graveyard'' Versus Map (Acheive by Completing ''Graveyard'' With VF-1A)

Superior Defense Medal: Unlocks ''Greystone'' Versus Map

Gold Nova Medal: Unlocks Nothing

RDF Supernova Medal: Unlocks ''Patriot'' Paint Design and ''City in Space'' Versus Map (Acheived by recieving 3 ''Gold Nova Medals'')

Robotech Marksmen Medal: Unlocks ''Stealth'' Paint Design

Wolf Leader Medal: Unlocks ''VF-1R'' and ''Wolf'' Paint Design

Tuna Head Medal: Unlocks ''Female Armor''

Jolly Roger Medal: Unlocks ''Skull-One'' Paint Design and ''Bursting Point'' Versus Map

Normally you can only use the special veritech armor (Super Veritech, Armored Veritech, etc.) you can only use them in space missions. However this was overlooked and can be used. Begin a space-mission with the special armor equiped on your veritech, beat the space mission, when the mission is over you can select Continue, you will continue to the next level (or a level you have not beaten yet) with the special veritech armor still equiped!