On all these cheats you MUST pause and be holding the L and R buttons the whole time.
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
X, Y, Up, Down, Give Gandalf 1,000 EP
Y, Up, B, A, Bring Gandalf to level 4
Y, X, X, X, Unlocks Frodo for use.
Y, Up, Down, X, Brings Frodo up to level 2
You have to have beaten The Cracks of Doom to get, Merry, Pippin, and Faramir.