As with pastorp I've probably done all the travelling around the US to hunt that I'll probably do. I will be 60 in a week or so and am in good health, I have just done all I want at the moment..but that could change before the day is out...hehehe. 99% of my hunting takes place on our property, consequently I'm not as bound to what might be available in a store as I may have been at one time. However, I have no memory of that ever being a consideration. I'll mention three because I have all three and for my purposes any of them is more than adequate. My problem is always choosing whether or not I want to shoot smokeless or black powder. Black powder almost always wins out. My first bought is an Imman. Meffert drilling from 1936 and is in 16 X 16 over 7 X 57R. I can't imagine a person needing anything more in the lower 48. My second is another drilling, a Thieme und Schlegelmilch in 16 X 16 over 9.3 X 75R Nimrod. Although it is proofed for smokeless I shoot black in it and it usually gets the nod between the drillings. For both drillings I have an einstecklauf in 22LR so that makes them even more "all around"...if such a thing exists. 22LR being one of my few concessions to smokeless powder. The third is a combination gun and is not proofed for smokeless and is in 16 X 10.5 X 47R. The T&S and the combo gun are used the most, the Meffert I simply enjoy owning for the most part....I do not recall the last time the rifle was fired.
I have yet to see a 12 bore drilling I want to carry all day long. I grew up on 16 bores and they always did the job with a lot less weight, fuss and muss. Still, the 12 bore is like the 30-06, neither are EVER wrong and for those who do not reload both are available just about anywhere. I reload, cast all my bullets and have more than ample experience with case forming so the odd and obscure cartridges are no problem and in fact I prefer them. All smoothbore chambers, except the Meffert, are still 2 1/2 and I use MagTech brass hulls loaded with black.