We like puzzle boxes! The easy-to-carry, easy-to-hide-things-in boxes are always so creative. They are decorative to perplex your mind, and complex for you to solve.
Take for example the puzzle box in Shadow at the Water's Edge: this one's a slider sort of puzzle. It is a simple concept that has you fingering the panels of wood in the right order to release the mechanism. Or think about the more tricky puzzle box from Curse of Blackmoor Manor: five of the six sides of this cube-shaped box have individual solutions. You need to know the answers before switching the colors and adjusting the stage of the moon.
Look here, I have a designer's sketch of the early stages of this box design:
Wouldn't it be cool to have your own puzzle box to store secrets or items? What would you hide inside?