Here's an attempt at Sansa's necklace bead from the the Darth Sansa scene in Game of Thrones season 4. It measures approximately 70mm across and 10mm tall, and is a little flatter on the bottom than the top so printing will be easier.

This would make an excellent tutorial object in 123D Design - create a cylinder with 35mm radius & 10mm height, create a cylinder with a 25mm radius, move the small one to overlap the big one, subtract the small one from the large, create a 10x10x50mm rectangle, merge, then fillet the edges.