Hmmm. Mysteries. I'm partial to Maine's Oak Island. Legend says Captain Kidd buried treasure there, then booby-trapped the whole place. There's a very interesting article about this on the Smithsonian site.
About Ripper speculation, I read a fascinating book by Patricia Cornwell which uses forensic examination of admittedly limited and sometimes degraded samples that still exist. Can't recall the title, though, but it's something like "The Ripper Case Solved." Regardless, Cornwell makes some interesting points.
I wish they'd find Jimmy Hoffa's body simply because virtually every square foot of New Jersey is under suspicion!
But my favorite mystery? The human brain! What is imagination, for instance? Where does it all come from?
"And the postman sighed as he scratched his head, you really rather thought she ought to be dead..."