File this under the "neat stuff" gift ideas. A gravity-defying game using 15 cardboard chairs that come in book format (comes with one constructed for reference; other require assembly). Made in spain, the Stacking Chairs Game
is for ages 8 and up, though I know plenty of adults who would love to get this as a gift. Great for the budding architect or brother-in-law who likes puzzles and games.
Pico Pao, Stacking Chairs Game