Ghost In The Shell: Stand Alone Complex Codes -

Completion bonuses
Successfully complete the game to unlock a movie viewer option and a mini-game featuring Tachikoma.

Special Tachikoma
When playing through a level, look for a yellow/orange box-shaped robot carrying a red and white fan. If you kill him, you will be rewarded with a special Tachikoma part when you complete the level. You will know if it was the correct robot by seeing the "Tachikoma part obtained" message appearing after it dies. 

Weapon bonuses
Successfully complete all single player mode levels with a character to unlock his or her custom weapon. After unlocking it, the weapon can be used by any character.