The Con Codes -

Boneyard
Defeat Boneyard (Team Phantom) in Class D Story mode to unlock him in arcade mode.

Cinder
Defeat Cinder and her team in Class A Story mode to unlock her in arcade mode.

Hardcase
Successfully complete arcade mode to unlock him in quick play mode.

KFJ
Defeat KFJ (Team Rogue) in Class B Story mode to unlock him in arcade mode.

Mask (Jeet Kune Do)
Complete arcade mode under the hard difficulty setting with a Jeet Kune Do fighter to unlock him in quick play mode.

Mask (Kickboxing)
Complete arcade mode under the hard difficulty setting with a Kickboxer to unlock him in quick play mode.

Mask (Street Boxing)
Complete arcade mode under the hard difficulty setting with a Street Boxer to unlock him in quick play mode.

Mask (Tae Kwon Do)
Complete arcade mode under the hard difficulty setting with a Tae Kwon Do fighter to unlock him in quick play mode.

Mask (Wrestling)
Complete arcade mode under the hard difficulty setting with a Wrestler to unlock him in quick play mode.

Reina
Successfully complete story mode.

Shaman
Defeat Shaman and his team in Class B to unlock him in arcade mode.

Smoke
Defeat Smoke and his team in Class C to unlock him in arcade mode.

Bonus quick play mode characters
After unlocking a character for quick play mode. Highlight the "Random" option at the character selection screen and press Circle until that character appears.

Bonus items
Defeat Cinder's (Class A), Shaman's (Class B), Smoke's (Class C), and Bonyard's (Class D) teams to unlock items used by the corresponding team leader.