DAM,

Sorry, but Americans are very used to "loaded" questions on this subject, questions meant to promote controversy rather than answers.

Ok, so, for a "loaded" answer: In your very hypothetical situation, if we were legally allowed only one firearm, it seems likely that the first order of business would be to get our rights back, and to disabuse whatever tyrannical regime was in power of the notion that any legitimate government, that is, a government that derives it's power from the consent of the governed, can remain legitimate and disarm the very people from whom it's power derives.

That being the case, it would seem that the answer would be one's choice of combat arm; battle rifles for most of us, who would anticipate having to make the point in combat, perhaps pistols for those in postitions to more effectively act covertly.

It's not a coincidence that Americans have the rights they do.

My original draft of this post went further into detailed choices, but I sense that this is getting uncomfortably off-topic for the focus of this website and forum, and it's a focus I support.