Playing with one bulb of my giant hourglass I fell on these water drops.
They are also very satisfying shapes to admire and to handle. They are strong and resistant.
You can even build the small one with 132 long rods (Geomag kids).
Add a plinth on one side or the other and you have a cute tree or a hot air balloon.
[Edit]: 297-Water drop Howto and 132-Water drop Howto.
(click on the pictures to enlarge)