Pause the game and hold L+R, then enter one of the following codes to enable the corresponding effect:
Get all upgrades: Up, Down, Y, B
Invincibility: B, X, B, Up
Devastating: Y, Up, Y, Down
Max health: B, B, X, X
Unlock Target Indicator: Down, X, Up, B
Aragon's 4 Hit Combo: Up, B, Y, Down
Frodo's 4 Hit Combo: Down, B, Down, X
Gandalf's 4 Hit Combo: Down, Y, Up, X
Gimli's 4 Hit Combo: Y, B, Up, A
Faramir's 4 Hit Combo: A, B, Up, A
Lagalos' 4 Hit Combo: B, Up, Up, Down
Play as Brobot: find the Brobot Postcard in Level 2
Merry's 4 Hit Combo: Y, A, B, B
Pippin's 4 Hit Combo: A, A, Down, X
Sam's 4 Hit Combo: Up, Down, Y, Y