Kasumi:
Kasumi has different hairstyles depending on what button you press at the character select screen. For her normal ponytail press A, for a braided ponytail press X, and for her hair to be unbound, press Y. To unlock Kasumi's hidden costume, complete all the exercises with all the normal characters in Sparring Mode.

Hayabusa:
While selecting Costume 2, press X for the White "Storm Shadow" version of Hayabusa's ninja outfit.

Hitomi:
While selecting Costume 1, press X. Hitomi will take off her jacket to reveal her tanktop.

Zack:
To get Zack's hidden costume, get 20 wins in survival mode with Zack.

Brad Wong:
While select Costume 2, press X for a reddish version of his outfit.

Tina:
While selecting Costume 1, press X to see Tina where a green top and leopard print pants.

Bass:
While selecting Costume 2, press X for a shirtless Bass.

Leon:
While selecting Costume 1, press X for a shirtless, bandolier wearing Leon.

Bayman:While selecting Costume 1, press X for a blue beret, non-vest wearing Bayman

Jann Lee:
While selecting Costume 1, press X to see Jann Lee wearing black pants and yellow shoes. Also, while selecting Costume 2, press X for a yellow version of this kung fu outfit. (The following has been submitted by Count3rGeko: To get Jann Lee's bouncer costume, play survival mode and pick up a silver Xbox after defeating someone. Note: This may take several tries.)

Lei Fang:
Lei Fang has three different versions of her Costume 1. For a white version press Y, for a blue version press X, and for a black version hold the L Trigger and press X, Y, or A.

Christie:
While selecting Costume 2, press X for a purple version of Christie's suit.

Helena:
While selecting Costume 2, press X for a black version of Helena's dress.

Hayate:
While selecting Costume 2, press X for a green version of Hayate's ninja outfit.

Ayane:
While selecting Costume 2, press X for a white version of Ayane's dress.