Virginia Postrel directs us to this more-revealing-than-you-might-think question. Look here. But I cannot fathom their decision to rank the Gambian flag number one. My personal favorites have long been Brazil ("Order and Progress", maybe you have to have been there) and Haiti, in part for the story of how they took out the white from the flag of France. Japan and Switzerland are good too, iconic you might say. The moon and star in the Turkish flag for a long time seemed cool to me.