Enter these codes at the main menu (with the New Game and Load Game options)
Cheat Effect
Left, Up, X, Up, Right, Y Classic Duke
Right, Up, Down, Down, Y Classic Scarlett

G.I. Joe Unlockables
Achievements

Complete each achievement to get the allotted gamerscore.
Unlockable How to Unlock
Baroness (25) Defeat Baroness (P1 only)
Destro (25) Defeat Destro (P1 only)
Firefly (25) Defeat Firefly (P1 only)
Storm Shattered (25) Defeat Storm Shadow in all three secret arenas (P1 only)
Strike Commander (50) Defeat every wave in all Satellite Strike mini-games (P1 only)
Strike Lieutenant (25) Defeat every wave in one Satellite Strike mini-game (P1 only)
Battle Master (75) Collect and spend all 130 possible Battle Points (P1 only)
Hack 'n Slash (20) Finish a level using only melee attacks on ground troops (P1 only)
Sloppy Joe (10) Achieve the worst rank on a level without going Man Down (P1 only)
Man Up (20) Complete a Jungle or Tundra mission without going Man Down (P1 only)
No "I" in Team (20) Complete mission with higher than 50% Dual Targeting kills (P1 only)
Half the Battle (10) Collect 50% of all File Cards (P1 only)
File-o-phile (35) Collect all File Cards (P1 only)
Classified (25) Collect all Intel Cards (P1 only)
Lost & Found (25) Collect all G.I. JOE Contacts (P1 only)
Triplets (25) Pick up all three types of Point Multipliers in one mission (P1 only)
Arctic Completed (50) Complete all Arctic missions (P1 only)
Desert Completed (50) Complete all Desert missions (P1 only)
Jungle Completed (50) Complete all Jungle missions (P1 only)
M.A.S.S. Destruction (50) Destroy the M.A.S.S. Device (P1 only)
Yo Joe! (10) Purchase two G.I. JOE contacts (P1 only)
All G.I. JOE Contacts (50) Purchase all G.I. JOE contacts (P1 only)
Combat Rock (10) Complete a mission using only Combat class characters (P1 only)
Go Commando (10) Complete a mission using only Commando class characters (P1 only)
Bevvy o' Heavy (10) Complete a mission using only Heavy class characters (P1 only)
Girls Night Out (10) Complete any mission using female characters only (P1 only)
Gimme The Keys (10) Drive every G.I. JOE vehicle in the game (P1 only)
Code Cracker (10) Gain access to a Combat Soldier Class Ability door (P1 only)
Nimble Access (10) Gain access to a Commando Class Ability door (P1 only)
Lost Keys (10) Gain access to a Heavy Class Ability door (P1 only)
Turret Syndrome (20) Operate the turret in every vehicle in the game (P1 only)
Double Barrel Roll (10) Perform 10 barrel rolls in unison in any level in co-op (P1 only)
Hardcore G.I. JOE (50) Complete every Mission on Hardcore Difficulty (P1 only)
Higher Score (10) Replay a mission and earn a higher score (P1 only)
Launch Money (10) Launch 50 enemies into the air and kill them (P1 only)
Acceleration Celebration (10) Activate the Accelerator Suit three times in any mission (P1 only)
Accomplished Mission (25) Gain the highest Mission Ranking (P1 only)
It Takes Two (10) Complete any mission in 2 player co-op (P1 only)
COBRAAAA!!! (25) Purchase all COBRA characters
Side Mission Completist (20) Complete all Sub-operation Missions
Arishikage Attack (10) Complete any mission using Snake Eyes and Storm Shadow
Lovers' Quarrel (10) Complete any mission using Baroness and Duke
The Tables Have Turned (10) Complete any Arctic, Desert, or Jungle mission using any COBRA character