Tarot Cards
Tarot cards have long been thought to be the tools of psychics and fortune-tellers. While some did pick them up for that purpose, they were originally designed to preserve knowledge that the Roman Catholic Church was trying to surpress. The sysbolism of the cards has much to do with Grail lore, and includes ideas of Christianity the Church had banned as herictical, such as the persistant belief in Mary Magdalene as the wife of Jesus, and information about their desendants.
The spade, club, diamond and heart of today's playing cards derive from the original Tarot cards, as well as the Joker.