I built this singlespeed up after finding a really great deal on the tires.
Other parts mostly out of my parts bin.
Frameset: 1986 Schwinn Passage
Crankset: All-Terra mountain triple with only it's 30T chainring
Freewheel: 17T ACS
Wheels: Old, beat up Performance hubs, Mavic MA-2 rims, double-butted spokes. I've had this wheelset forever.
Tires: Kenda Happy Medium 700x35
Should be fun. I'll probably get it dirty this weekend. Brakes are marginal at the moment, but that should just add to the excitement. Need to get some better pads.