My new favorite idea: the hideaway ring by the Seattle based John Welden. Wanting to create something extra-special for his wife, the crafter came up with an idea of a plain band with a twist.
While closed, the ring seems a a plain titanium ring.
When opened, it reveals a single, bright diamond.
Welden created the mechanism as well as some of the tools needed to create this ring himself. Read more on his webpage.
This piece is beautiful as well as ingenious.