Have to do it but I might have to give up my 45 for a 223. I guess I would have to if I had to limit down to only 5 categories of firearms use.
fun and plinking
you cannot beat a .22 for inexpensive fun, availability, and versatility of little critters.
sigh...I would have to give up my 45 acp for a 357 magnum. This is the reason why. the 357 magnum and the 45 is a good man stopper, however the 357 has more longer range applications and more ammo versatility. And I would go with a revolver not an auto if I could only choose one handgun. A revolver not only for its reliably of eating anything you could feed it, but operational reliability and its endurance. A revolver does not compress springs until it is actually being fired, so the springs on revolver will last longer than an auto that has to compress springs on a ready position. This of course assuming parts are hard to come by. I would like to have both 357 and 45 but I could not justify having 2 handguns when I have an option to have another rifle.
It is hard to beat a .223 for it's accuracy, availability, and for a hunting caliber from anything from rabbit to a coyote. It also makes for a great personal protection weapon.
large game hunting
has to be the .308, just because of ammo availability and it will take down anything in North America without a problem.
anything with wings
12 gauge for ammo availability and it will take down anything with wings, and again it makes for a good personal protection gun.
theres my 2 cents