Naruto: Clash Of Ninja

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

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)
tightplus and Gaara Uchiha.

Rock Lee:
Successfully complete single player mode without losing a life. Defeat Rock Lee in battle to unlock him as a playable character. Note: When you defeat Zabuza with no continues, always attack him up close.
ZacComicMan.

Sharigan Kakashi:
Unlock Kyuubi Naruto, then successfully complete the game in single player mode as him. Then, successfully complete the game in single player mode as Kakashi. Highlight Kakashi at the character selection screen and press X or Z.
tightplus.

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.
Gaara Uchiha.

Alternate costumes:
Highlight a fighter and press Y at the character selection screen.
tightplus.

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

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

Difficulty 4:
Finish in first place in Survival mode.

Hint: Kakashi: Stronger special:
When you press Y to do Kakashi's special hold it down. It will charge and he will attack automatically. The attack will go farther and do more damage.
Sameer Syed.

Hint: Naruto Kyuubi form: Easy win:
To win easily press Forward, B(5). 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.
John.

Hint: Sakura and Haku: Projectile combo:
With Sakura, after pressing A for shuriken, press A again for another, then A again for a finsher to the combo. Haku can do sort of the same thing, however after pressing A initially you can only press A once more.
John.

Hint: 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.
Inuyasha47.

Note: This will not work on Haku.
madooley.

Hint: Sharigan Kakashi: Easy wins:
When playing as Sharigan Kakashi, wait until your opponent uses his strongest move and send it back at him. For example, when fighting Rock Lee, when he uses the Foured Lotus Technique you can use it against him.
ZacComicMan.

Hint: Sasuke: Combo:
One of Sasuke's best combos is B(4), A. The Fire Jutsu causes big damage and if timed correctly, you can kill the opponent with this combo.
sean morris.

Hint: More shuriken/projectiles:
Hold A to charge up shurikens/projectiles to throw more of them.
John.

Hint: Shorter fireball Justu:
Press Forward + A to do fireball Justsu.
odigie.

Hint: Substitution Jutsu:
To use Substitution Jutsu, press R or L while taking damage or being hit. This is also useful when the other player grabs you. Note: You need a green level Chakra.
Jake.

Hint: Easy wins:
In single player mode, the best way to win is to use continuos attacks in an elaborate combo, mostly with characters that are stronger physically rather then using Jutsu. For example, as Rock Lee, continuously pressing B and giving your opponent No Mercy is good. You will take hardly any damage. However, with characters that are better with projectiles and Jutsu such as Kyuubi Naruto, it is easier to win if you have a good amount of Chakra.
ZacComicMan.

In survival mode, choose Sasuke and continuously use either the B(7) or B(4), A combos on the opponent without giving them a chance to stand up. Your Chakra gauge should fill up with only two or three uses of the combos. If the opponent is not defeated yet, then use his special move directly next to them, as they are almost standing up all the way. If you use it too early, it will not hit them.
madooley.

In survival mode, choose Kyubi Naruto and keep pressing B(6), or go forward and continuously press B. You will get his special move after only one or two combos. You do not need to use it, but you can save it for the next battle.
madooley.

When using Naruto, Sasuke, etc., press Y when close to an opponent. Then, press Up + A to throw Kunai while the opponent is still in the air.
cam truong.

Note: This trick works best when your opponent has no Chakra and you have maximum Chakra. Choose Sasuke. Make sure there is enough room for a full throw. Throw, then use Fire Jutsu. Continue and when out, jump and attack with Kunai. If done correctly you should throw your opponent, burn him or her, then precisely when the "afterburner" quits, you will hit him or her with a Kunai. This will take a lot of health away from your opponent.
SLCannon.

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

Hint: Character voices in sound test:
After completing single player mode twice with any character, go to "Omake" (extras), then "SE Effects", then "Character Voices". That character's voice is now unlocked, and says a number of phrases.
ItachiTyler.

Hint: Secret dialogue:
The best way to view this is to go to "Play Against Computer" mode. Chose Naruto as your character then select the CPU character as Sasuke. Select a level to play on. When it says "Naruto Uzumaki vs. Sasuke Uchiha," hold X until the beginning dialogue starts. They should both look at each other and say "I've been waiting for this, I wanna fight you" at the same time.
Cal Lawrence and wingedsabre323.

Whenever you have a battle with Kakashi vs. Zabuza, they will say "Give it up, what lies in your future is defeat". Zabuza will say, "Bear witness to my technique". When you play as Sharingan Kakashi, he will always say, "It'll be over in a flash, nothing personal". However, if you put Sharingan Kakashi and Zabuza together they will still say, "Give it up, what lies in your future is defeat" and "Bear witness to my technique".
wingedsabre323.