I'm really charmed by these wooden puzzle boxes: You can store stuff inside the inner metal tube, but to open the box you need to rotate the wooden outer cylinder to guide an internal peg through its wooden maze.
Apart from being pretty to look at and fun to use, puzzle locks — at least, the ones that aren't demonically hard — have a sort of gentle utility. If you get good at opening one, you can do it pretty quickly, while for any neophyte it'll be an incredibly slow experience; yet it is not impossible for a neophyte to open it, so in a pinch someone new to the device could do so.
It's an interesting set of affordances. Granted, I can't think of many situations that precisely call for those affordances, but gimme some time to ponder it, heh.
(Found via The Awesomer)