At the mode select screen, highlight practice mode and press start, up, up, forward, up, forward,up, start. Then go to the practice mode and you'll see a new bonus game!
CPU M. Bison (Vega), Akuma (Gouki), and Garuda
Select expert mode. Highlight M.Bison/Vega, Akuma/Gouki, or Garuda on the character selection screen and hold Select while choosing that character. The border around the character will turn from white to yellow to confirm correct code entry. Note: This code may only be enabled after a specific number of points have been accumulated. Press Start instead of Select for the Japanese version of the game.
Cracker Jack's bonus weapon
Choose Cracker Jack at the character selection screen, then immediately hold Up + Square + Circle + R1 + R2 until the match starts. Cracker Jack will have a bat during the fight.
Fight against Akuma as final Boss
Fight through the game normally, with the following criteria: have at least three Perfects, do not lose any round, and have at least five Super Combo victories. M. Bison will appear and then get beaten down, with Akuma appearing in his place.
Fight as Priestess Hokoto
Select alpha mode on the options menu. Select the default setting in the controller settings menu. Using any method, unlock Evil Hokoto. Select Evil Hokoto by pressing Hard/Fierce Punch. Quickly press and hold the following buttons simultaneously: L2 + Start + Medium Punch + Weak Punch. Continue holding those buttons until the first round starts. Priestess Hokoto has different armor and uses a priestess flail as a weapon. However, she does not have a different ending.
Hidden characters
At the mode select, highlight the practice mode and press start, up, forward, down, forward, start. Instead of going to the expert mode to release all the secret characters, this code will bring them all out for you.
Bonus Game...