Friday the 13th...

http://www.snopes.com/luck/friday13.asp
http://en.wikipedia.org/wiki/Friday_the_13th
http://www.fridaythe13thfilms.com/
http://people.howstuffworks.com/friday-thirteenth.htm
http://www.oldsuperstitions.com/
http://www.lyricsfreak.com/f/frank-sinatra/55625.html

"Luck is my middle name," said Rincewind, indistinctly. "Mind you, my first name is Bad."
(Terry Pratchett, Interesting Times)