From Wikipedia:

A Friday occurring on the 13th day of any month is considered to be a day of bad luck in English, German, Polish and Portuguese-speaking cultures around the globe…
…The fear of Friday the 13th is called paraskavedekatriaphobia (a word that is derived from the concatenation of the Greek words Παρασκευή, δεκατρείς, and φοβία, meaning Friday, thirteen, and phobia respectively; alternate spellings include paraskevodekatriaphobia or paraskevidekatriaphobia) or friggatriskaidekaphobia, and is a specialized form of triskaidekaphobia, a phobia (fear) of the number thirteen.

I think friggatriskaidekaphobia might be the best word ever.