Some one brought up the micro sized 9mm Luger pistols.
For example you can get a Kimber Micro Carry in .380 ACP at 13.4 oz or you can get the Kimber Micro 9 in 9mm Luger at 15.6 oz.
Given the apples to apples operating systems, and the significantly more powerful 9mm Luger round, the Micro 9 is going to generate more recoil, both actual and perceived, than the .380 ACP.
Unless someone is willing and able to shoot the Micro 9 as well as the Micro Carry, the Micro 9 is a bad choice for them - they will be better served getting more round on target in less time with the smaller .380 ACP.
I don't regard the .380 ACP as my first choice as a primary self defense handgun, although I do carry it as my only pistol in some specific situations. I have however carried the PPK/S and more recently the Kimber Micro Carry as a back up on a regular basis. Both are small enough to carry in a pocket holster. The Kimber Micro Carry has the advantage of being about 10 oz lighter, and it's a little shorter, but the PPK/S, despite the sharper recoil, has an edge in accuracy.
I considered the Mico 9, but it doesn't shoot as well as either of the above pistols and with a additional .4" in length, it's just a bit too long for pocket carry as a backup.
And it also fails in one role of a back up pistol in our household - handing it off to my wife. My wife does not conceal carry. While she shoots, she does not shoot nearly as much as I do and is not as proficient with heavier recoiling pistols. She can however shoot a Kimber Micro Carry just fine. Consequently, if we end up walking into a situation where we need to withdraw, I can hand the Kimber Micro to her in its pocket holster and she can then lead the retreat while I cover our retreat with my primary pistol.
In other words, how you plan to use a small pistol should also come into consideration when choosing the pistol.