The Lord of the Rings: The Return of the King Cheats for GameCube

Pause Your Game hold L,R and press Y,X,X,X to unlock Frodo.

Unlockable Cheats
Beat the game to be able to unlock the following cheats. To activate the
cheats pause game-play and hold L and R buttons and press the following combinations
Restore Health:
B, B, X, X
Invicibility:
B, X, B, Up
Perfect Mode:
X, Down, Y, A
Always Devastating:
Y, Up, Y, Down
Have Upgrades:
Up, Down, Y, B
Infinite Second Weapon:
B, B, Down, X
Targeting Indicator:
Down, X, Up, B

To have access to the following cheats you must first beat the game.
To activate the cheats pause game-play and hold L + R before entering the
following codes:
Have Upgrades:
Up, Down, Y, B
Restore Health:
B, B, X, X
Perfect Mode:
X, Down, Y, A
Always Devastating:
Y, Up, Y, Down
Targeting Indicator:
Down, X, Up, B
Infinite Second Weapon:
B, B, Down, X
Invicibility:
B, X, B, Up

On all these cheats you MUST pause and be holding the L and R buttons the whole time.
Aragorn:
Up, B, Y, A, Give Aragorn 1,000 Experience Points
Y, B, B, Y, Replenish Aragorn's Arrows
Up, B, Y, Down, Aqcuire four upgrades immediately, when leveled up high enough. Upgrades: Dark Deliverance, Shield Cleaver, Lightning Strike, and Swift Justice.
Legolas's Gimli's and Sam's cheats can be used more then once.
Legolas, Gimli, and Sam:
A, Y, Up, A, Give Legolas 1,000 experience.
X, X, Y, A, Give Gimli 1,000 EP
T, A, Down, A, Give Sam 1,000 EP
Gandalf:
X, Y, Up, Down, Give Gandalf 1,000 EP
Y, Up, B, A, Bring Gandalf to level 4
Unlock Frodo:
Y, X, X, X, Unlocks Frodo for use.
Y, Up, Down..

First you must beat the game then pause during a level and hold down L&R
Restore Health B,B,X,X
Perfect Mode X,down,Y,A
All Upgrades up,down,Y,B
Infinite Missile B,B,down,X
Invulnerable B,X,B,up