A climbing wall for a kids bedroom. Up until now the twins have shared a bedroom. They've been more than happy with this arrangement, but now they've started school (in separate classes) and we've been encouraging their independence .
I'm not a fan of bunk beds but if you have them and you need to create some protection from the energy then this is a good idea. Built in Bunk Beds, plumbing pipe ladder, love the curtains - privacy in a shared room.