Azrek said:
Bond's original gun was a .25 cal Beretta. The concept of Bond was he was an assassin who was at close range of his target and a .25 to the head or heart would be enough to kill the person he needed to remove. And a silencer on a .25 would sound like someone coughed instead of a massive bang.
All these other guns are dandy, but Bond was never designed to fight an entire army thus there is no reason to have all these handcannons when a .25cal pistol can be concealed in your coat very easily.
So I stick to the Walter or the .25cal beretta for such work.
Plus Bond killed very few people with the beretta anyway (at least compared to the films).
I don't mean to bust anyone's bubble, but secret agents are not typically provided with guns or even taught how to use them. There was one case in which an agent, unable to convince the top brass to provide him with a firearm, had to go about buying his own just so he could shoot an enemy agent trailing him. When it comes to actual wet work, agents may use guns or any number of creative means.
Saying all that, I'd use a Volcanic repeating arms company lever-action revolver (.41)