by ColinBB, published
I've taken ferret7's http://www.thingiverse.com/thing:1340
and optimized for a necklace and/or keychain.
Rather than drilling a hole after printing, I put the hole in the design.
I print with 0 extra shells and 10-20% infill. Bend your own wire for a keychain or necklace. Or just buy a key ring.