Here are few Gopro Hero 3 must have gadgets. They should be in every Gopro box. Fortunately they cost just few bucks on ebay.
GOPRO ALU RING , very usefull if you don’t want to loose your precious camera. It is even easier to mount it. And looks cool. After installation camera is still water proof. Tested 😉
LENS COVER You need that to protect your lens. In package are 2 pieces. One for case and one for camera. Usefull when you charge your camera and when you throw it in your backpac.
REMOTE STRAP: This should really be in the box when you purchase gopro. I can’t see how remote can be usefull without this strap.
http://www.flickr.com/photos/96040100@N07/11709893626/