He could sell scuba gear to a shark.
He could sell needles to a porcupine.
He could sell snowshoes to a camel.
He could sell water to a drowning man.
He could sell salt to a slug.
He could sell snow to Canadians.
He could sell hair shampoo to a bald man.
He could sell pork to a Jew.
He could sell an Anfield season ticket to an Everton fan.
He could sell clothes at a nudist retreat.
He could sell binoculars to an eagle.
He could sell coffee to a Mormon.
He could sell an airline ticket to an aerophobic.