The limited edition of Call of Duty Black Ops included a code for avatar clothing, but for male avatars only. Due to complaints from female gamers who bought the limited edition Activision have released a couple of multi use codes.
These are for use for female avatars only, and even work if you don't have a Gold membership:
Black Ops Flight Suit
Either enter on the dashboard, or via https://live.xbox.com/en-GB/RedeemToken
(Copy and paste!!)
Thanks to the CheapAssGamer forum for these.