The abnormal fear of the number 13, of course. Very common. And in effect today. Also common is coulrophobia, the totally justified fear (and loathing) of clowns (see Killer Klowns from Outer Space, Shakes the Clown). Not very common, but problematic, is the fear of knees, called genuphobia (see James St. James, who’ll assuage your fear). And Todd Radnitz has anemophobia, the fear of draughts, which is why he keeps the door to his cubicle shut. I think.