Bugge!

There's a school of thought that toys with only one possible function can - by their very nature - limit the imagination. Given the way that children can extract seemingly endless enjoyment out of anything from a few pebbles to an empty box, I can see where they're coming from.

Bugge (page in Norwegian) is an example of this way of thinking. Seven organic shapes can be stacked or combined in whatever ways the children prefer; its creator, Ingse Galtung Døsvig, says she was surprised by the uses the kids found for it, above and beyond what she had imagined herself. The shapes became dens, a shop, a tunnel, and lots more besides.

Bugge is a student project, from Bergen's national Academy of the Arts. However, if you are interested to read more, there are several links at the end of the article linked to above (which, by the way, can be read via Google Translate).