William Shakespeare
While you've certainly heard of William Shakespeare, it might be surprising to find that he may not have existed. Scholars have yet to figure out how a glover's son from the countryside managed to enter the literary world. Theorists suppose that he may have been a ghostwriter, Francis Bacon, or Christopher Marlowe, an essayist and a playwright from the same era.
Jack the Ripper
Between August and November of 1888, at least five prostitutes were mutilated and violently murdered in London. These crimes introduced the mystery of Jack the Ripper, who sent an anonymous letter to a London news agency confessing to the murders. Although it has been over a century, the identity of the killer is still under wraps.