I-Ninja cheats and cheat codes for Gamecube

Skip stage:
hit Start to pause game play, then hold R and hit B, B, B, X. Release R, then
hold L and hit Y, Y. Release L, then hold and hit R, B, B.

Upgraded sword:
hit Start to pause game play, then hold L + R and hit X, B, X, Y, Y, B, X, B.

Big head mode:
hit Start to pause game play, then hold R and hit Y(4 times). Release R,
then hold L and hit Y, Y. Hold R + L, then hit Y, X, Y

Finish Current Mission:
Hold R Button, B, B, B, X, release R Button, Hold L Button, Y, Y, Release L Button,
Hold R Button, B, B.

Unlock Battle Arena
Earn all the Grades, then you will get the Master Grade and unlock the
battle arena.

Sword list:
Notice that the sword color changes in the your belt changes.
1. Ninja's Sword
2. Golden Sword
3. Jade Sword
4. Sapphire Sword
5. Fire Sword
6. Soul Sword

Healing:
If you are low on health, try to find some weeds and chop them down. Notice
that your Rage Ability switch will gradually increase. Keep chopping down
weeds and you will soon be able to use your "Ninja Revive" to heal yourself.

Rage skills:
1st skill: Ninja Berserk
2nd skill: Ninja Revive
3rd skill: Ninja Shuriken
4th skill: Lightning Rage