Bishop from Naples who is the patron saint of blood bank workers. That might seem weird, but in Naples there is a glass vial of his blood which turns from powder to liquid twice every year - on his feast day September 19th, and on the first saturday in May (maybe he's a fan of the Kentucky Derby). The thing is, the few times that the powder hasn't turned to liquid, disaster has struck, including in 1980 when an earthquake in November killed 3000 in southern Italy. His blood liquified right on time in the year 2000.
The substance has been identified as blood, even though the vial is closed.No one knows why it liquifies. Scientists are baffled.
known aliases include St. Januarius. (No, I don't know why I'm obsessed with the whole patron saint thing.)