Don't be deceived by the simple appearance of Hamayama's "Nutcase" puzzle; this thing is a definite brain teaser. This cast metal puzzle offers two challenges:

1. Disassemble the case to reveal a hidden compartment with small nuts inside.
2. Reassemble the puzzle but with the words on the bolts in reverse order (i.e. nut-case → case-nut)

This puzzle will probably take a while for you to solve on your own. Of course, you could always read the included solution if you get stumped, but where's the fun in that?

Get the puzzle for $10 on Amazon.