You're Tyrion's champion in a fight against the Mountain That Rides, Gregor Clegane. You can choose any real-world weapon. The only restriction is that it has to be used in the relatively small arena. Stuff to consider: Explosives? Will you be hit by the fragmentation? Maybe reconsider. Bullets? Could Gregor's armor stop the bullets long enough to kill you? Machine gun? Could you actually bear the recoil to use it effectively? GO