@Draugnar - The Right to Bear Arms is not an extension of the Right to Life (be it natural or not) but part of the Rights to Liberty (which is not about the IF contained in the former, but about the HOW). As such the potential cases enumerated by u are NOT a justification for the R2BA.
Positivistic logic aside, even teleologically speaking ur justification is not correct. If indeed u are implying that some kinds of guns (and their use) have a specific purpose in specific situations of self-defense, than one must also weigh in their usefulness. I.e., of course u might wish an AR-15 or heavier stuff against a crazy SWAT - but even in the unlikely event that u will be targeted by such an individual, u might not be capable to handle even the heaviest weapon in an appropriate or meaningful manner unless u have undergone similar training. Second, concerning ur other examples: such situations r highly different from Holywood movies or computer games. It is in such surprise situations not bigger gun - smaller gun, but stress reaction against stress reaction. Most of the time though, the robber would win, were he really a danger for ur life (and probably even so). The fireman situation calls even less for a gun, but for some psychological strength and some MA techniques at best.
On the downside: widely accessible firearms, esp. semi-automatics, etc. increase the risk of an intruder being armed with guns instead of muscles or knives, increase the risk firemen having not just axes, increases the risk of people who would otherwise (not nice, but still) burn cars, destroy windows and so on to get over a divorce/job loss/… use their hand guns and automatics instead, and last but not least - allow the potentially crazy SWAT to have the arms at home (which should not be the case) he is trained to use.
This considered, the R2BA is counterproductive for most of its presumable purposes. Applying things such as precautionary principles, it is maybe the most dangerous solution to the problems it is intended to solve. I understand people who like weapons, I do, too. But I also think one needs to be honest to oneself and about the situation. I therefore would be against an R2BA. But I am not American, so I just wonder…