Super Street Fighter II X

Play as Akuma / Gouki
After selecting the speed (if you can), keep the cursor on Ryu for three seconds. Now move Rx4 to T. Hawk and then pause for three seconds. Move L once to Guile and pause again. Now move D and R to Cammy and wait again. Now move Lx4 and U back to Ryu and pause for the final three seconds. Now press and hold START instantly followed by all three P buttons at the same time. A shadow will replace Ryu's picture. This code is quite hard to get right.
 
Super Characters
To pick the Super version of a character, pick the character with any button, then enter the following joystick motions and then press jab once complete.
  Ryu      - RRRL           T. Hawk  - RRLL 
  Ken      - LLLR           Cammy    - UUDD 
  E. Honda - UUUD           Dee Jay  - DDUU 
  Chun Li  - DDDU           Fei Long - LLRR 
  Blanka   - RLLL           Balrog   - RLLR 
  Zangief  - LRRR           Vega     - LRRL 
  Guile    - UDDD           Sagat    - UDDU 
  Dhalsim  - DUUU           M. Bison - DUUD