Use The Bosses
On the Mode Select screen, press L, R, Up, L, L, Down, R, R. Select your mode, and you will now be able to choose from 12 characters instead of only 10.

9 Continues
On the Mode Select screen, press Left, Right, Left, Right, L, L, R, R, R. The next time you lose a match, you will notice that you now have nine continues.

Raise Attributes
On the Mode Select screen:

For two Attributes, press
L, L, L, R, L, R, L, R.

For four, press
Up, Right, Down, Left, Down, Right, R, R.

For six, press
Right, Down, Down, Left, Up, Right, L, R, L, R, L, R.

Disable Dizzies
On the Mode Select screen, press Down, Down, Left, Up, Down, Down, Left, Up, R, R, L. You'll here a noise if entered correctly and the code will stay in effect until the game is turned off.

Disable Throws
On the mode Select Screen, press R, Right, L, L, Left, Left, R, R. You'll here a noise if entered correctly and the code will stay in effect until the game is turned off.