All Working Naruto: Clash of Ninja Cheats - GameCube

Rock Lee
Play the game in story mode. Use no continues and defeat Zaibuzan. Defeat Rock Lee when he appears to unlock him.

Kyuubi Naruto
Unlock Rock Lee, then successfully complete the game in single player mode two times with all characters. Then, highlight Nartuto at the character selection screen and press [X] (for the orange suit Kyuubi) or [Z] (for the red suit Kyuubi).

Shaningan Sasuke
Successfully complete the game as Sasuke under all difficulty settings.

Unmasked Haku
Successfully complete the game in arcade mode as Zabusa under difficulty 3. Then, highlight Haku at the character selection screen and press [X] or [Z]. When Haku is hit in the face, or is hit and takes a lot of damage, Haku's Mask will fly off his face.

Sound test
Successfully complete the game with all default characters in single player mode to unlock the "Sounds Test" option in the Omake menu.

Attack Power 4
Finish in first place in Time Attack mode.

Difficulty 4
Finish in first place in Survival mode.

Naruto Kyuubi form: Easy win
To win easily press [Forward], [B]x5. Before your opponent gets back up, use it again. If you get hit, press [R] and use Substitution Jutsu. You will probably have lots of Chakra. Note: You must have green Chakra level to perform Substitution Jutsu.

Sharingan Kakashi: Use enemy's super
Play as Sharingan Kakashi. When your opponent uses their super, use your counter. If done correctly, Kakashi will do his own version of your opponent's super. Note: This will not work on Haku.

Sasuke: Combo
One of Sasuke's best combos is [B]x4, [A]. The Fire Jutsu causes big damage and if timed correctly, you can kill the opponent with this combo.

More shuriken/projectiles
Hold [A] to charge up shurikens/projectiles to throw more of them.

Shorter fireball Justu
Press [Forward] + [A] to do fireball Justsu.

Turn auto save on
Make sure "On" is orange and "Off" is white.