Xenosaga Episode III: Also Sprach Zarathustra cheats and cheat codes for Playstation 2

Unlock the Swimsuit mode option
Finish the game once, then go to the "Memory Code" event viewer to 
access to the Swimsuit mode option.

Extra costumes:
Finish the game then save the cleared game. Load the cleared save 
file to access to the Chaos Flawless and Allen Swimsuit outfits.

Unlock Vector costume for Shion:
Have a completed saved game file from Xenosaga Episode 2 on your 
memory card. Load Xenosaga Episode 2 saved game when starting a 
new Xenosaga Episode 3 game to unlock new costume.

The Business District Gate code: 
Go to the right as far as possible on Miltia's map (when you are 
able to move around). You should find a treasure chest on 
top of a building. To open the chest, enter "5150" as a code.