I've standardized on NATO calibers. I've gone heavy on 9mm, as I prefer PDW's in my AO, due to terrain and vegetation. I've got quite a bit of 5.56, and I'm still using it, and 9mm for practicing, as shooting is a perishable skill. I've gone heavy on 12 gauge and .22LR. I don't have much .50BMG, mostly due to the cost, though I've started accumulating reloading components.
I guess I would end up settling for 4-5 firearms.
Definitely a .22LR long gun with an appropriate suppressor, probably a Ruger Precision Rimfire or a Savage MKII.
9mm PDW, either an Uzi, Ruger Charger 9mm pistol, or a PAK pistol in 9mm, because my wife can easily handle them, again with a suppressor
Handgun probably a H&K VP9, because of ammo availability, though a H&K .45 USP could be a possibility
Sniper/anti personnel weapon Barrett model 99 in .50 BMG
CQC firearm, a Keltec KSG 12 gauge shotgun, which gives the user the option of loading a tube of buckshot, and a tube of slugs, or a tube of birdshot, lots of versatility.
In any case, I've got numerous .22lr firearms and AR's, because 2 is 1 and 1 is none. I don't like the AR platform, as I've mentioned before, I prefer the Steyr AUG and H&K platforms.
In my AO folks are still shooting, in fact, I heard shots earlier this afternoon. I'll be practicing again later this week. As I tell my wife, those shots are the sound of freedom.