I've just put together my first single speed from a 1992 Cannondale M1000. I'ts about as light as I could afford to make it, coming in at a fraction under 9kg. Exotic carbon forks, 3T Team Doric carbon seat post, Charge saddle, carbon bars, Syncross stem, Ritchy foam grips, XT v brakes with LX levers. Tioga Surefoot V1 pedals, Suntour XC Comp cranks Schwalbe1.5 City Jets. Rides nice . Definately not one for the purists
I did one of those as a fixie back in 2005! I used an ENO hub, which wasn't entirely satisfactory (it tended to creep round and lose chain tension). I did 132 miles on it on the night of the 2008 Dunwich Dynamo, because we got a little bit lost.