Okay boys and girls this is a creativity exercise. Give me your best wild jerry-riged end of the world guns or melee weapons. I am not looking for practicality here just awesomeness.
To get this started my exambles are the double barrel shot gun with crossbow mounted on top that Willem Dafue uses in Day Breakers. And the Remington 1740 which is the result of sticking a left and a right handed Remington 870 shotgun together. (Yours don't have to be preexisting I am just uncreative.)