Tekken 4

Fight as Eddy Gordo:
Successfully complete the game in story mode as Christie Monteiro. Then, highlight Christie and press RP (Triangle) at the character selection screen. Eddy Gordo plays exactly like Christie.
RazmatheShadow and Brian LaCount.

Fight as Miharu:
Successfully complete the game in story mode as Ling Xiaoyu . Then, highlight Ling Xiaoyu and press RK (Circle) at the character selection screen. Miharu looks like Ling in her schoolgirl outfit from Tekken 3 and Tekken Tag Tournament and plays just like her.
RazmatheShadow and Brian LaCount.

Fight as Ling Xiaoyu in school uniform:
Successfully complete the game in story mode as Ling Xiaoyu. Then, highlight Ling Xiaoyu and press RP (Triangle) at the character selection screen.

Fight as Panda :
Highlight Kuma at the character selection screen, then press RP (Triangle) or RK (Circle).

Fight as Violet:
Highlight Lee at the character selection screen, then press RK (Circle).

Unlocking all characters:
Successfully complete the game with the indicated character to unlock the corresponding fighter.
Ogre Samanosuke and shoppin-tonight.

Kazuya to unlock Jin Kazama
Christy to unlock Eddy Gordo
Xiaoyou to unlock Kuma/Panda (Miharu is also selectable)
Yoshimitsu to unlock Brian Fury
Bryan to unlock Violet, if Jin is already unlocked; otherwise, Jin
Violet to unlock Combot (and Violet can now be Lee)
Nina to unlock Lei
Marduk, Paul, or Law to unlock Hiehachi (unless all others are unlocked, in which case anyone unlocks him).

Dojo stage:
Successfully complete the game in Tekken Force mode.

Statue stage:
Successfully complete story mode as Steve Fox. Note: This is the stage where Steve fights Nina in stage 7. Also, the music on this stage is the same that is found in the original Tekken.

Theater mode:
Successfully complete the game in Story mode.

Ranking password:
Successfully complete Time Attack, Survival, Tekken Force, or Training mode. Hold Square + Triangle and press Up/Right to display a password that corresponds to your rank.

Alternate victory pose:
After winning the final round in a match, hold Square, X, Circle, or Triangle during the replay to view a different ending pose for each button.
Renzokuken Kid and Electro_Maz.

Choose opponent's costume:
When the versus screen appears, hold X or Triangle to select your opponent's costume.
Michael Obed.

Marduk
Triangle: Black jacket with his name on it
X: No top, Green & Purple shorts

Hwoarang
Triangle: Military costume
X: Tae Kwon Do costume

Xiaoyu
Triangle: Pink dress
X: Red & white bellytop

Steve
Triangle: Blue top with flowers on
X: Boxing costume

View move names:
Press Select during a match then enter a combo to see its name.

View practice mode move percentage:
Enter practice mode with any fighter. Press Start and select the command list. Hold L1, L2, R1, or R2 to see how many times that move has been done in practice mode.

Battle replay mode:
Successfully complete the game under the easy difficulty setting to unlock battle replay mode. This helps to teach your enemies' attack patterns. It is also a good way to show off to friends. Press Select after it is unlocked at the end of your fight. Note: This only works on two round fights, survival, time, and team attack.
D0mINIcan001.

Hint: Combot: Metal sound:
Hold Down before any round starts to give Combot a metal sound.
Meccablue720.

Hint: Paul: Combo:
Paul has two moves that make good strategy for winning. First, do the Hammer Of The Gods (Left + Up + Square + Triangle). As your opponent is getting up, press Right + Up + Square + Triangle. This takes away about 75% of your opponent's health.
Bud.

Hint: Paul: Secret taunt:
Crouch down without moving and wait for three seconds. Paul will perform his Taunt Stands.
Leon Lee Ganeshan.

Hint: Steve Fox: Easy win:
Use the Rocket Launcher (press Toward(2), Square).
Wallshadow12.

Hint: Xiayou: Skirt peek:
In practice mode, select King then choose either Xiayou or Miharu as the practice dummy. When you knock Xiayou down, switch her to the controller while she is on the ground. Have King flip her over to her stomach if she is not already in that position. Then, get in front of her head and push her by walking to raise her skirt up higher.
courtclee.

Hint: Yoshimitsu: Secret taunts:
Get in the Meditating Healing (Down + X + Circle), into the Levitation (X + Circle), then release of the buttons before pressing Punch. Release Square to laugh; Triangle to say something; or Square + Triangle to says something.
tardedape.

Hint: Yoshimitsu: Strong attack:
Press Away(2), Circle to do a stab that takes out a chunk of your opponent's health.
Riff200.

Hint: Off the wall attack:
Stand near a wall with your back to it and tap Back(2), Up/Back. Your character will jump off the wall and attack. This works well in Tekken Force mode.
RG7.

Hint: Jumping, ducking, blocking, and sidestepping:
When your opponent attacks you with a low blow, like a sweep kick, etc. jump and attack. Not only will you avoid your opponents attack, but you will have just kicked his face into the dirt. When you opponent attacks you with an attack at your body (above the shoulders), duck and attack. With mid-attacks, you should block in most cases or use a side step.
ASFCommander1989.

Hint: Wall-less stage:
Play one entire game in time attack mode as any character. In the very next game, play in story mode with the same character. When you reach Heihachi at the Arena stage, there will be no walls.
Ellery Ross, Jr..

Hint: Red Hot Chili Peppers reference:
In the fourth and final stage of Tekken Force mode, the Mishima Fortress, fight your way through the stage until you reach an open balcony area with two "bird watchers" standing looking over. Continue to fight in this area until a squad of "assassins" appear. Their names are Anthony, Flea, Chad and John, which are the names of the members of the band Red Hot Chili Peppers (Anthony Kiedis, Flea Balzaris, Chad Jones, and John Frusciante). The fifth member of the squad of assassins, Dave, however is not a member of Red Hot Chili Peppers.

Hint: Tekken 2 reference:
While choosing the "Statue" stage at the character selection screen and the match starts, you will hear background music based on Tekken 2. After the match ends and selecting the "Statue" stage again, you will hear more background music from Tekken 2 while the match restarts. The background music for the "Statue" stage may vary.
Edgar Caragay.

Glitch: Opponent gets extra damage:
When fighting in a specific level such as The Jungle, choose Christie or Eddy and face any character. Then, get them in the water and next to a log. Keep break dancing, and if you do a powerful enough attack, they will fall back and hit themselves on the head with the log, causing extra damage. Note: This works with all characters but is easier with Chrisite or Eddy.
fridge928.

Glitch: Mist Wolf Combo:
Do the Mist wolf combo with Lee/Violet while your opponent is in the air. You will notice a strange rubber band effect. This would count as an air throw.
david larmour.

Note: There are codes that will conflict with certain aspects of the game. The "Infinite Health" code will not allow you to win a Survival series. This is because your health will have to eventually go down to win. With the code activated, you will continue to fight people indefinitely. The "P1" and "P2 Are Always Charged" code does not work. The "Infinite Time In Tekken Force Mode" code is not a wise option because it will not let you leave the room you start in on level four. Also, If there is an abundance of codes active for this game, it will lock up.
Lonnie Cross.