Mobsters have used .22LR for hits. The bullet enters the skull and just bounces around without exiting.
Aside from that crudity, I would not recommend for self-defense, but .22LR is a good choice for small game.
I carry a 45, 9 mm, a 22, and when I’m heading up North for the weekends I generally have an AR in the truck with me. I’m not paranoid but I am prepared with a gun at every door. I travel for work so you never know what situation you’re going to be in.
The Zodiac Killer used .22LR for his first attack on a young couple parking in a lover's lane at night. He killed the teenage boy with a single shot to the head; he then ran down the fleeing girl and dropped her with four or five (can't remember which, offhand) shots to the back.
For his next kill he used a 9MM. Presumably he had learned something.
Growing up my Dad and I put a dent in the local ground squirrel population with .22LR. Of course they breed like rabbits and were back in force the next year tearing up the yard again.
A .22lr is how we dispatch livestock in these here parts.
My father was a lifelong shooter. In his last few years, he switched from a .45 to a 9 mm and then a .22LR for self defense. The key is choosing the right tool for the individual and for the job, and sometimes that tool is the .22 - even for self defense.
The only things that bounce around inside one's skull are silly notions.