Bought a "fixie" today. A fixie is a fixed gear bicycle, also known as a track bike. It's got one gear, and often (though not always), no freewheel or brakes.
I bought a KHS Flight 100. Only thing I've done so far is to replace the non-freewheeling hub with a coaster brake hub. I did this to preserve the clean lines of the bike (saves adding front/rear caliper brakes), while also saving my knees. As fun as "skip stopping" and "skid stopping" are, those non-freewheeling hubs are brutal on the knees, and I really want to keep mine healthy!