For my own part, I’m going with 4 because the thread title permits it. I’m going to also pick from guns I already own—mostly because I can’t afford to pay attention, let alone buy more guns.
Option 1:
1. Henry Octagon Frontier lever action in .22 S/L/LR
2. Mossberg 590A1 w/ 20" barrel, 8+1 rounds capacity
3. 20" AR-15
4. G17 or G19…either would be fine.
Option 2:
Same as above except #3 is a SCAR 17S in .308 instead of an AR-15. Why my SCAR, and not one of my bolt action .308s? Because it’s at least as accurate as most bolt actions (1.5 MOA with M80 ball, even better with 168 grain match); it’s good out to about 800 yards (which is further than I would need to shoot anything/anybody); it’s modular and can be tailored to my body dimensions (plus a folding stock); it is relatively lightweight for a "battle rifle"; and it has 20 round mags giving it higher capacity. My main complaint about the SCAR is that it doesn’t take STANAG mags without spending a LOT of money on an after market lower that takes AR-10 mags, and the FN mags are now selling for $60 apiece or more. Fortunately, I have some FN mags…maybe 10 or 12…but I could use more.
Although I own a couple of .22 pistols, I never considered making one part of a 4-gun combo because anything I’d want to shoot with a .22 would be better served by the higher velocity and better accuracy of a .22 rifle.
I picked my pump action shotgun over a semiauto I own and actually prefer shooting, because the pump has 2" more of barrel (and sight radius) for slightly more velocity, and carries an additional 8th round in the magazine. Velocity never hurt anyone…except maybe the shootee…and slugs turn it into a legitimate 150 yard big game gun. If money weren’t an issue (for now), I’d be happy to try and pick up a longer barrel that accepts chokes for my semiauto, and forego the extra round of capacity the pump gun offers. Then I’d have a shotgun I like shooting, that could be as easily used for hunting as it could be used for SD.
9mm Glocks need no explanation.