The goal of gaining FullMount is Brazilian Jiu Jitsu 101 and a great place to be for MMA or in a real fight. Obviously in a real fight you can rain down strikes to your opponent's face but there are a number of submissions there to end the fight.
In the video below Keith Owen, a Pedro Sauer Black Belt, goes over a number of submissions that he uses from the position. There is a complete game in the video below so check it out.