Street Fighter 3: W Impact.

Fight as Gouki (Akuma)

Highlight Sean at the Street Fighter 3 Second Impact character selection screen and press Up.

Fight as Gill

Successfully complete Street Fighter 3 or Street Fighter 3 Second Impact under any difficulty setting. Highlight Sean at the character selection screen and press Up, Up.

Fight as Yang

Highlight Yun at the Street Fighter 3 character selection screen and press any Kick button.

Play as shin akuma

You got to get 3 perfects or more and then beat gill with each round with a super move. Then you fight akuma and you have to beat him the same way.