I have to bang the drum again for the Seven-Barreled Nock Volley Gun:
https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcRQ0cyL4qO-kJw0R4HJv1dZO0kPBsYEM0xvaMMBuSq8Db3gHq8uPvXu9y9w
Another thing that'd be an absolute laugh(particularly in CQB) would be the duckfoot pistol, again courtesy of Mr. Henry Nock of London :
https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcQFko1l3_SdWjGbZGoFvmbkbq2esKcqX6670eEigJMHrc5eBbEGRGBjeQNE
Then, in no way being a CoDsofter,I actually like the idea of a ballistic knife; I know that they're not practical but hey