I don’t post this because I condone the use of fixies in the city. I post it because these bikes are kind of rad. Sure, fixies are actually impractical in the city, especially one like Seattle, where I live, but there’s something to be said for removing mechanical elements until all you have left is a unicycle with a front wheel and handlebars. More info at Inner City Bikes.
(Oops, I missed the fact that this is actually a 1:1 freewheel, not a fixie; i.e. You can coast down a hill with it and the pedals stay still. Much more practical.)