CheatOgre.com: Dead Or Alive 3

Play as Ein
1. First Beat the game with every character.
2. Take Hayate through Survival or Time Attack Mode, and place.
3. Enter your name as "Ein".
4. You can now play him in any mode but Story.

Watch clips
When you play as story mode after you have beaten OMEGA you can watch a small clip. At the main menu you can watch the clips of all the characters that have beaten story mode.

Beat the game with each character to see each ending
Unlock 'Real Ending' with On/Off Option. Beat the game with everyone. The last character you beat it with will have the staff credits attached to the ending. Once that's done, you can decide if you want the credits on or off the endings in the Game Settings Screen.

Kasumi Hair Trick
When picking Kasumi, press Y for her long hair, A for her pony tail.

Unlock Ein's third costume
Complete Time Attack in under 6 minutes

Unlock Zack's third costume
Beat 20 people in Survival Mode .

Unlock Kasumi's third costume
In the Sparring Option, Perform all of Kasumi's moves under the "Exercise" Option. Once the game awards you the "Complete!" award, you'll have the costume