Good design fits the bill. Good design performs the task/s it was set efficiently.
Sometimes, however it takes a little serendipity to elevate the work from something that works to something that excels. Accidental design can, like the name suggests, occur at pretty much any time with any design but it is more likely to happen when the designer keeps an open mind.

 

Don Norman (user centered design guru and acclaimed author of The Design of Everyday Things) neatly summarises it thus:

 

The value of a well designed object is when it has such a rich set of affordances that the people who use it could do things that the designer never imagined.

 

For instance, take Twitter. It was originally designed to allow SMS conversations to take place between groups rather than individuals. It wasn’t intended as a global communications tool that changed the way real time information spreads, but it was so well designed (and, in the words of Norman, with such a rich set of affordances), that it paved the way for a piece of beautifully realised, if accidental, design.

 

Design as well as you can and keep an open mind. Who knows where it will take you.