.22 Rifle, preferably a short Ruger 10-22. If not, a bolt action or single shot... for reliability.
12 gauge shotgun, with a single shot, pump or bolt action
.243, bolt action (Savage or Remington)
Luckily, at least in present times, I don't have to pick just three. A list of 5 would have included an AR and a handgun... but it would still be difficult to decide.