A necklace, shaped like the infamous mask.
I looked all through the Google Sketchup Warehouse to try to find a good file I could modify, but most of them were folded 2d files, and while trying to modify the one's that weren't, I realized I'm not good enough at anything but Solidworks to be able to modify them for my purposes, so I drew one up myself.
I stole the ring size from http://www.thingiverse.com/thing:1764 because the ring I had already fit through that to attach it to a chain. I wish I could say I was also inspired by it, but unfortunately the person who commissioned me to design it had no knowledge of that thing (though I printed her one in the meantime).
You will need one of those little ringy things seen in the thumbnail, I stole that one off of an old free keychain I got somewhere. They shouldn't be too hard to find, or see merlinjim's comment below for instructions on how to make your own.
Then just print and attach to your favorite chain. (Makes a great gift too)
I like to print from an SD card when I'm printing things that I want to look nice, but I found that it wouldn't let me build from the card because the filename was too long. Just shorten the filename if you're having this problem too.