If it’s for personal carry, a subcompact .380, is probably the most popular…
I usually recommend mace.
If you have to use it, spray it, in a figure 8 pattern, focusing on the nose, and eyes. But. You shouldn’t use it, in a closed space, or indoors.
Your number one weapon, is your brain. Try to stay aware of your surroundings, and what situations, you get into…
@Josie , is correct. A 9mm, is a fast bullet. It is not likely to stop an attacker. A .380, is basically the same projectile, as is a .38 cal…
If you want knock down power, go with a .40 cal/10mm, or higher.
A revolver, is nice choice. It will hold less rounds, but is more dependable. It’s also less safe, though. It always has a round chambered. Therefore, you could shoot yourself, while drawing it.
NEVER draw, with your finger, on the trigger.
It’s been proven that a person who has a knife, can usually close the distance between you, before most can draw a firearm.
It’s honestly best, not to carry a firearm…
Unless you are highly trained…