Ghost in the Shell: Stand Alone Complex

Successfully complete the game to unlock a movie vieweroption and a mini-game featuring Tachikoma.

Clear every mission in the 1-player story with a character to unlock that character's personal custom weapon. You can get a weapon for every character in the game, and any weapon you unlock can be then used by the other characters as well.

When playing through a level, look for a yellow/orangebox-shaped robot carrying a red and white fan. If you kill him,you will be rewarded with a special Tachikoma part when you completethe level. You will know if it was the correct robot by seeingthe "Tachikoma part obtained" message appearing afterit dies.
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When an enemy drops a weapon that you don't have in your inventory, pick it up, and make sure to finish the level while still holding it. When you start a new level the weapon will be permanently added to your inventory.

Just beat the game with any character in order to unlock a SpyHunter like minigame featuring Tachikoma, and a Movie Viewer that let's you watch all of the game's cutscenes again.

If you start a mission with only a handgun equipped, at the end of the mission you will be rewarded with that same handgun in its dual form - 2 of the same gun that can be equipped at once, only needing 1 weapon slot to hold.

You can use this method to unlock a dual version of each of the standard handguns in the game.

Play through a level with only a handgun. At the end of the level you will be given the dual wieldable version of that handgun. You will be able to equip both of the handguns in one weapon slot.

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.