A very cool hipster on a fixie, or fixed gear bike. Personally, I think these things are about as functional as a Penny Farthing. But that's just my opinion. Going by how many of these things I am seeing out and about, my opinion counts for diddly-squat.
There is something attractive about the stripped down nature of this type of bike. No gears, brakes, lights, computer, water bottle, pannier, mudguards or anything that is extraneous to simply riding a bike. Me - I like all those things. I'm careful not to go gadget-happy, but this guy isn't even carrying a puncture kit. There's riding bare bones, and then there's just silly.