Different costumes and more o - Anarchy In The Nippon 2
Different costumes and more options:
Complete the game in single player mode then highlight a fighter and enter Down at the character selection screen to choose a new costume.
Slow motion replay:
Just hold Circle before the replay begins.
Play as Boss:
Complete the game using all ten characters. Then with the controller keep going to the far left or far right (past the last charachter) at the character select screen.