risks: You can get banned if you are noticed so don't add to much at a time.
Le Fluffie:http://www.megaupload.com/?d=PO9YLYCD
Horizon: [ Register or Signin to view external links. ]
Tutorial: Step 1: Move your profile to usb. Just go into system settings/Memory/Hard drive/Profiles/ Now choose
the profile you want to mod and move to memory stick/Usb
Step 2: Now move the memory stick to your computer and open Xtaf Xplorer.
Step 3: choose content and keep choosing until you reach the end should begin with E000
Step 4: now choose extract and extract to your desktop.
Step 5: dont close xtaf xplorer just shrink. Now open Le Fluffie.
Step 6: In the top left corner choose file/Desktop/then the file you extracted earlier.
step 7: a new window should open now choose Profile
Step 8: now choose unlock all this will unlock all achievements for your played games and add gamerscore.
Step 9: If you have other GPD'S you can add them by going to add games then choosing them then unlock all.
Step 10: Open Modio Drag the file from your desktop and choose Rehash and Resign.
Step 11: now reopen Xtaf Xplorer and choose inject/Desktop/the modded file Eooo
step 12: Delete the top file which is your old one. Close all programs.
Step 13: move the usb back to xbox and move profile back to hard drive.
Step 14: sign in and enjoy the Gamerscore.

Risks: Can get banned if you go around bragging.
Ezgt2.1:http://www.megaupload.com/?d=VO7I02XV
Horizon:
Tutorial; Step 1: Move Profile to usb as explained above and once again extract your profile using Xtaf Xplorer
as explained above.
Step 2: open ezgt Go to little guy in corner and choose open/Desktop/Then add profile Eooo
Step 3: go to add and choose your gamertag you want. now save to Desktop.
Step 4: Open the file you just created and go to the end now open modio and drag and drop the last file
you come to unto modio now rehash and resign.
step 5: now open Xtaf Xplorer and back up until you reach content. Now click on content to next folder and choose inject folder
/Desktop and the folder you made with ezgt.
Step 6: close everything move usb back to xbox and move profile back to hard drive.
Step 7: you must sign in to modded name go into say mw2 go all the way to xbox live and it will say .
"this profile can not play on xbox live and it will give option to sign into another profile.
Now sign int original profile you modded and go into xbox live multiplayer and enjoy the new gamertag

Risks:You Lose your avatar awards and can get temporary ban
Xtaf Xplorer:http://www.4shared.com/file/QlO5MiSe/USB_XTAF_GUI_v32_BETA.html
Step 1: Open xtaf Xplorer and Xtract your profile as explained above.
Step 2: open Horizon and at the top choose Profile Mods/Avatar color.
Step 3: Chose open file/Desktop/Now your profile.
step 4: your name should appear in box now chose your colors and save.
Step 5: reopen xtaf explorer and go to profile Eooo now inject the folder from desktop and delete old one.
Step 6: put your profile back on xbox and enjoy your new avatar.

Risks: None i know of.unless you corrupt your file
Tools:
Xtaf Xplorer:
Modio:http://www.megaupload.com/?d=YWROQMJW
Tutorial: Step 1: Play one short game of campaign or just kill yourself and save.
Step 2: find the game save on hard drive and move to usb.
Step 3: open xtafxplorer and find the file named savegame.svg extract to desktop.
Step 4: open modio and drag the file from desktop unto modio.
Step 5: Choose mod file and go to it.
Step 6: select save when done.
Step 7: now reopen xtafxplorer and inject modded file back into savegame.svg spot.
Step 8: Delete old file from xtafxplorer.
Step 9: now move back to xbox and enjoy the campaign.

Risks: None i know of unless you corrupt your file.
Tools:Xtaf Xplorer:
Modio:http://www.megaupload.com/?d=YWROQMJW
Tutorial Step 1: first move one of your themes from hard drive to usb.
Step 2: now open xtafxplorer and find the file that starts with 000 now open to next folder.
Step 3: shrink xtafxplorer and open modio.
Step 4: once in modio choose other tools and theme creator.
Step 5: add the pics you want and save to desktop.
Step 6: reopen xtafxplorer and inject the file into the folder after the three 0's
Step 7: Move back to xbox and choose your new theme and enjoy