These awesome mario inspired adaptations of popular metro/subway systems are not only amazingly designed, but quite accurate. The DC Metro even includes the soon to be opened Silver line (phase 1). The maps I'm familiar with are surprisingly accurate and functional, containing all of the info of the original. I say, let's make a push to get these adopted as the official maps!
Dave's collection of posters, designs, and jerseys are worth a look. Very clever and quite awesome.
San Francisco/Bay Area