One foot per nano-second!
Translating that into metric units it is about 30cm in a billionth of a second (where this is a UK billionth - namely one thousand millionth of a second).
Not many people know that! But for some of us it is actually a useful rule-of-thumb in our daily work.
You might also like to surprise someone with the unit of a micro-century. Just between you and me, that is just over an hour. Business meetings should generally limited to a micro-century. In that time, light manages to travel about 750 million miles.