If James Bond has a signature drink in the books, it would have to be the Vesper, since it was first popularized through Fleming's novels. A better balanced drink by the way than a vodka martini, which is why way too many restaurant "vodka martinis" are chilled, diluted vodka without a statistically significant amount of vermouth.
Although if one wants to look at the novels, Mr. Bond drinks both gin and vodka martinis. However, he drinks more whisk(e)y drinks than either, and also brandy classics like the stinger.
Besides, I wouldn't trust the drink-making expertise of a fictional character that shakes Martinis. Do you even know the rules about when to shake and when to stir?
Martinis have gin. And vermouth.
