At the 'Main' select the 'Cheat Codes' option and enter the following codes to unlock the corresponding effect. Enabling these codes will prevent you from earning Achievements and saving the game.

ALL Upgrades:
Press LB, Y, LB, B, X(2)

Invincibility:
Press RB, A, X, LB, X(2)

Infinite Turbo:
Press B, LB, X, RB, A, Y

No Weapon Overheat:
Press LB, X, A, LB, Y, LB

Always in Overdrive Mode:
Press LB, B, LB, A, X, RB

Special Kills Only Mode:
Press B(2), RB, B, A, LB

Low Gravity Mode:
Press X(2), Y, LB, Y, LB

No Special Cooldown Time:
Press RB, X, RB(2), X, A

Extra Energon from Defeated Enemies:
Press Y, X, B, RB, A, Y

Increased Weapon Damage in Robot Form:
Press Y(2), RB, A, LB, Y

Increased Weapon Damage in Vehicle Form:
Press Y, B, RB, X, RB, LB

Melee Instant Kills:
Press RB, A, LB, B, RB, LB

Lower Enemy Accuracy:
Press X, LB, RB, LB, RB(2)

Press Increased Enemy Health:
Press B, X, LB, B, RB, Y

Increased Enemy Damage:
Press LB, Y, A, Y, RB(2)

Increased Enemy Accuracy:
Press Y(2), B, A, X, LB

ALL Shanghai Missions and Zones:
Press Y, LB, RB, LB, Y, A

ALL West Coast Missions and Zones:
Press LB, RB(2), Y, RB, B

ALL Deep Six Missions and Zones:
Press X, RB, Y, B, A, LB

ALL East Coast Missions and Zones:
Press RB, LB, RB, A, B, X

ALL Cairo Missions and Zones:
Press RB, Y, A, Y, LB(2)

Play G1 Ironhide in Single-Player Mode:
Press LB, RB, RB, A, B, Y

Play G1 Starscream in Single-Player Mode:
Press B, A, B, RB, Y, RB

Play as Decepticon Seeker Warrior MP in Decepticon based Single-Player Mode:
Press X, Y, X, LB, A, LB

Play as Autobot Protectobot Scout MP in Autobot based Single-Player Mode:
Press RB, LB(2), Y, X, A (does not work in Deep 6)

Select the 'Cheat Codes' option at the 'Main' menu and press B, A, B, RB, Y, RB to unlock G1 Starscream as a playable character. G1 Starscream can transform into an F-15 Eagle and serves as the Decepticon Air Commander.

These Golden versions of the characters which are only playable in Multiplayer become available options when you use the D-Pad to enter the corresponding codes at the 'Cheat Codes' option at the 'Main' menu.

Unlock Golden Megatron:
Press Down, Up, Right, Right, Left, Up.

Unlock Golden Optimus Prime:
Press Up, Down, Left, Left, Right, Down.