Widow Black's B&B Needle Nanny by Praiseworthy Stitching

It's intended purpose is to hold your needle for you when you're not stitching or quilting. Simply place your fabric between the two magnets and you've got the perfect resting spot for your needle.

You can also put the magnet on your lamp if it is metal and rest your needle there. 

Other uses include wearing it as a pin, using it as a scarf button, adding it to a hat for decoration, or simply displaying them as you build your collection.