1) The Zodiac Murders
One of the most unsettling and sadistic unsolved cases is of 'The Zodiac.' For two decades, the Zodiac Killer haunted and killed in Northern California. Although only 5 were directly linked to him, he has claimed to have killed 37 people. He gained popularity for sending letters to the newspaper - San Francisco Chronicle with ciphers which he claimed would reveal his identity, but none could be deciphered. One of his only codes which could be deciphered revealed the message that he loved killing. The police tried their best, but he always managed to outsmart them. Many books and movies have been based on him, the most popular being the 2007 movie - Zodiac, starring Jake Gyllenhaal, Robert Downey Jr., and Mark Ruffalo.