Destination Arcade is a free Xbox 360 app from Microsoft. This allows you to browse games featured in the marketplace. This may be of little intrest to you but if you like free Avatar items then it might.
Simply run the application to receive a white Xbox Live Arcade emblazoned hoodie for both boys and girls.
You can also unlock a purple dragon by viewing the details on any fantasy-based game (for example Magic: The Gathering)
Note: Whilst this application is only available in the USA you can still get these awards here in the UK (or anywhere else I would imagine).
Simply register an account with the US Xbox Live service, download the game to your Xbox and then run it with your desired profile.