1.
Mauser 98 or Brno 602 in .375 H&H, Zeiss 4x scope, low rings, claw mounts.
2.
S&W .22 revolver, with spare .22 Magnum cylinder, J frame, 4" barrel, adjustable sights (formerly known as their model 34 "kit gun" or, in stainless steel model 63, same gun otherwise).
3.
Westley Richards best grade drop lock double rifle, made to fit me, with double triggers, 26" ejector barrels, also in .375 H&H belted rimless magnum, classic express sights regulated for 300 grain round nose soft and solid, with spare 20 bore, 26" shotgun barrels, 3" chambers, ejectors, choked left side true cylinder and right side full.
Do I really have to explain why?
Ok, I will:
I chose the 20 because I suspect a .375 on the 12 gauge frame would be unnecessarily heavy, less elegant looking and less responsive for close range instinctive shooting.
The makers mentioned are all very much favorites of mine (vintage S&W anyway).
The rifle caliber mentioned is available both where I live and in Africa as well, not to mention effective for the things I will likely ever hunt or have to stop from clobbering me (grizzly are common where I live).
I actually own the Brno .375 H&H but with lever rings, not claw mounts (yet, heh heh).
Also own the revolver mentioned but without a spare cylinder (although such was available by special order in my time).
So, I own one each of the described revolvers.
(In the OP's scenario, I'd have to stay with one revolver and extra cylinder, no problem).
Anyway, one is the regular .22 rimfire caliber and it's otherwise identical twin is the .22 magnum caliber.
Both excellent small game hunting revolvers.
The .22 magnum can stand in as a defensive round, if I had no larger caliber handgun available.
It'd be even better for this if 60 grain flat nose solids were available for it.
(Not that the regular 40 grainers would not do passable work on attacking creeps, viscious dogs and such.)
For shotguns, I generally prefer cylinder bore for most bird hunting plus, slug shooting, when called for.
But, a reserve barrel with tight choke and #4 lead shot is handy for the odd longer shot.
I prefer to fire rear trigger first on doubles (so, left barrel) to avoid doubling by "strumming" the triggers in recoil.
Yes, neither the .375 or 20 bore modest recoil are likely to cause this but, it is my habit with all doubles, heavy kickers or not.
(Thankfully I'm not stuck with only 3 firearms, neither with any newer S&W revolver for that matter, )