Play As Akuma:
At the Player Select screen, press Up, R1, Down, L2, Right, L1, Left, R2. The code must be entered quickly for it to work. If it doesn't work, go to Guile and try again. When it works, choose Guile to play as Akuma.
Go to the Practice mode and press Start, then quickly press Up, Up, Right, Up, Right, Up and press Start again. If you did it right a message will say "Here comes a bonus game." Just enter practice mode for bonus fun!
Play as the 4 Secret Characters:
In the game selection screen, highlight the Practice option with the cursor and press Select, then Up, Right, Down, Right, then hit Select again. You should get the message "Here comes a new challenger" in small letters at the bottom of your screen. Go to the game and viola, there they are..
Cracker Jack 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.
Thanks to Revolution readers Andrew Macdonald, Chris Moody, Groovy_dude, Vaseem, Seyla Chin, Sephiroth17, Cloude, and Alex Lopez!