Street Fighter Alpha 3 Codes -

Fight as Shin Akuma/Super Gouki:
Highlight Akuma/Gouki at the character selection screen. Then hold Start and press A.

Fight as Super Vega:
Select arcade, training, or versus mode. Highlight Vega at the character selection screen, then hold Start and press A.

Select winning pose:
When you get a KO, immediately hold a Punch or Kick button. Different buttons will give you different poses. Note: Different characters have different number of poses.