Here's another vote for the H&K P7. The thing is, if you're down to only one gun, it's going to have to be like a swiss army knife, not the best tool for any one job, but one that will do many things and get you by. The P7M8 fits that bill for me, accurate enough for hunting or target, small enough for carry, enough power and speed for a fighting handgun. It is capable of filling every requirement, although no one would say it was the best hunting handgun, for instance, it will get the job done if that's all you have. That's why it would get my vote. Hope this helps.
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With my shield or on it...