For little stuff, grouse and such, either the .22 or 12 ga gets the nod.
For big game, either the .30-06 or the .338 Win Mag gets the nod. Either will work well on most game in BC, with the .338 getting the nod as the game gets bigger. It works just fine, with no more meat damage than the '06 on smaller big game (ie deer) as well.
Truthfully, there are a couple dozen perfectly good cartridges that will serve well as a deer to moose/elk rifle. Anything from 6.5 mm up to .375, that will drive a decent hunting bullet at upwards of 2300-2400 fps will cover a lot of hunting in BC. As the game gets bigger, larger calibers or higher velocity or both tend to be preferred.
The main factors to consider are the recoil tolerance of the shooter, the availability of ammo (or components), the cost of ammo (components as well) and the intended usage.
It is pretty hard to beat a rifle chambered for something in the range of a 7 mm-08 or 7X57 up to a .338 Win Mag for a do it all gun in BC. There are lots of options in here that all achieve pretty much the same result.
You would be hard pressed to beat a readily available cartridge such as a .270, .308, .30-06, 7 mm Rem Mag, or .300 Win Mag as a do it all gun. Ammo is relatively cheap, very readily available for all, guns are abundantly available and they will all work well for most hunting in BC. Picking one good gun, using it for everything for now, learning how it shoots and becoming very familiar with that gun will be a better choice than a gaggle of guns that you are unfamiliar with, just because the cartridge it is chambered for is theoretically the perfect choice for the game being hunted. It's better to place a good, killing shot with a smaller, less powerful round, than to gut shoot or miss with a big powerful manly magnum. This is especially true for less experienced shooters and hunters.
