The ace of spades  is traditionally the highest card in the deck of playing cards. In legend and folklore, it is also known as the Death Card. 

In Vietnam, entire crates of Ace of Spades cards were shipped by the company to U.S. troops as it was believed at the time (later proven to be a myth) that the Viet Cong soldiers were superstitious of the card and would flee battle at the sight of seeing it resting upon the body of one of their dead. (Source)