Pistol-caliber subcarbines
I have a Beretta Cx4 subcarbine in 9mm that takes 92 mags. I keep it as an HD gun, but my initial intent was to do so as a defensive firearm either me or my wife could use effectively. I think there's much to be said for it: Very compact, reliable with factory magazines, accurate at realistic ranges, much more stable and user-friendly than a pistol but retaining the same basic controls, etc. I've run a few defensive carbine courses with it, and it is very much quieter than the ARs. It was the only non-AR in all the classes I took.
Nonetheless, my spouse never really warmed to it, and she actually greatly prefers the M1 carbine. The Hornady FTX CD ammo for the M1 carbine, the Winchester JHP, and the Remington SP cartridges all give the carbine a lot of utility for HD or having along on an extended road trip through the country.