Go to "Main Menu"->"Extras"->"Preorder" and enter the following codes to unlock the corresponding cheat:
360378 - The Lost Blade of the Kusagari Clan.
360152 - Sora Katana of the Katakara Clan.
3582880 - Barracuda.
Gecko Codes, US
Keep in mind that the following codes work only when used with a softmodded Wii running the Gecko OS (or compatible homebrew application). These codes WILL NOT WORK without a compatible application.
Infinite cash (after getting cash)
Increase your focus quickly to disarm opponents. Use the Uzi. It fires a lot of bullets that do not do a lot of damage. Therefore, if you are out of focus and want to disarm sum1, shoot them with the Uzi for awhile. You should get enough focus back to disarm them without killing them. Try doing this if a leader comes in the room and you are out of focus. It makes tough rooms easier.
Once You learn how to focus, start using it right away. While in combat, focus as soon as you can and shoot the guns out of your opponent's hands (aim inside the white box). Now, shake the Wiimote Up and Down to disarm them. This will take them out of combat and give you about 50 respect per enemy. Also, if there is a leader in the room (an enemy with a circle above his head), disarm him immediately to make all other enemies in the room disarm, giving you a large respect bonus.