One of the five should be a shotgun, pump action or semi-auto 12 gauge. This would be good for home defense and even better for killing vermin or shooting small game such as rabbits, squirrels, or birds for meat. There also should be a .22 semi-auto rifle for plinking, target shooting and also for hunting small game. The ammunition is the most affordable you can get. Here are some guns to stick with:
The quintessential rimfire rifle. Useful for 22LR practice, and has a wide variety of aftermarket parts and customization possibilities. Also useful for the small game. I find the takedown model makes cleaning marginally easier.
Most popular centerfire rifle. Like the 10/22, has a wide variety of aftermarket parts, and the modular design makes it easy to find and replace parts you need to fix or want to improve. Proven track record and extensively tested design.
Mossberg 500 / Pre-Freedom Group Remington 870
Cheap, popular, reliable shotgun(s). Barrels can be swapped, giving you the option of using 18-inch barrels for home defense, 30-inch barrels for sporting use, rifled barrels for hunting larger game.
Fires the ubiquitous 9mm round, proven reliability, a wide range of aftermarket parts and support. Simple to use, easy takedown. Conversion kits to 22LR are available for cheaper practice.
5th gun: Up To You
You’ve got a rimfire rifle, a centerfire rifle, a shotgun, and a handgun; as I see it, these have you covered as far as utility goes. Anything else really just depends on your preference. You could get:
A rifle in a full power cartridge, like a AR 10 or a Remington 700.
An over/under shotgun for trap and skeet so you at least kind of fit in with the crowd, like a Browning Citori Lightning. The action of an over-under makes it easy to use sub-gauge adapter tubes, allowing you to shoot smaller gauge shells and some pistol rounds from an adapter tube that fits in your 12 gauge smoothbore barrel.
An autoloading shotgun like the Mossberg 930, Remington 1100, or Beretta A300
An autoloading pistol that doesn’t look gross/boring (sorry…), like a CZ75 or 1911
A revolver in .357 magnum
Personally, I like my old faithful 45 Colt revolver, and would not want to be without it. I have homemade reloads for it that make it as powerful as a .44 magnum and strong enough to take deer size game…OR I can use the standard cowboy type loads for more comfortable shooting. It is accurate and feels great in my hand. It is not concealable as it is heavy and has a 7 1/2 barrel, but it is great to carry in a holster around a ranch, farm, or woodlands.