This is my purpose-built all-road bike, a 1973 Raleigh Competition running a Surly Dingle 17/19T fixed cog with 42/44T chainrings, so I get a 70-in pavement and a 60-in gravel fixed gear. Someday I'll spend the money for a White Industries Dos Eno 20/22T freewheel for the flop side of the hub, giving me 60-in road-ish and 52-in single-track-ish freewheel gears. The tires are 35 mm Continental Cyclocross Speeds.
But honestly, I've ridden most of the fire and dirt and gravel roads in this part of South Carolina with 26-28 mm tires on this Mercian fixed-gear. Not too much of a handicap, really.