Good design begins by breaking rules. It challenges the suppositions that society places on an object's use and look. 

This set of built-in bunks (above) is a fine example of good design. The designers, Tim Barber Ltd., take a kid's furniture staple, the old rickety bunk bed, and beef it up by enclosing it, painting it an interesting non-kid color, and basically turning it into an architectural element in its own right.