 The most persistent theory (most usually attributed to a friend of    a friend who saw it posted on a message board by someone whose    brother had read a report of a radio interview with Tarantino    himself) is that it is Marcellus Wallaces soul. The story goes    that when the Devil takes a persons soul, it is removed through    the back of the head (this isnt part of any known religion, but    this is what the message board posters say). When we see the back    of Marcelluss head he has a Band