Almost every character has an alternate color to one of their costumes and a few have a hidden costume. Here they are:
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.
While selecting Costume 2, press X for the White "Storm Shadow" version of Hayabusa's ninja outfit.
While selecting Costume 1, press X. Hitomi will take off her jacket to reveal her tanktop.
To get Zack's hidden costume, get 20 wins in survival mode with Zack.
While select Costume 2, press X for a reddish version of his outfit.
While selecting Costume 1, press X to see Tina where a green top and leopard print pants.
While selecting Costume 2, press X for a shirtless Bass.
While selecting Costume 1, press X for a shirtless, bandolier wearing Leon.
While selecting Costume 1, press X for a blue beret, non-vest wearing Bayman
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 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.
While selecting Costume 2, press X for a purple version of Christie's suit.
While selecting Costume 2, press X for a black version of Helena's dress.
While selecting Costume 2, press X for a green version of Hayate's ninja outfit.
While selecting Costume 2, press X for a white version of Ayane's dress.
To get Ein's hidden costume, finish Time Attack with Ein in under six minutes (totalling eight battles).
Unlocking Ein and Random Select:
To unlock Ein from Dead Or Alive 2, finish Story Mode with every character. After the final credits roll (save the game byentering and exiting the Options Menu) go into Survival Mode with Hayate and play so you can put your name in the rankings (minimum three victories). While at the ranking screen, enter EIN as the name. You will unlock Ein playable in every mode except Story Mode, and you'll also unlock a Random Character Select feature.