1) comfortable to wear, therefore, must be small and lightweight
2) ease of use
For me, it all adds up to a Ruger LCR revolver. 15 ounces (unloaded), goes bang every time (nothing to rack, unlock, or jam), eight round capacity. Yes, in .22 caliber. Don't need a howitzer. Don't need a laser or special optics. You're not going to aim so much as point. I figure if it is in self-defense you are at close range. (Otherwise, your best bet is to seek shelter.) You want to get your shot off before he aims at you. A .22 bullet to the gut/head, etc. is enuff to discombobulate anyone, even someone high on angel dust. Bullets cheap and (relatively) plentiful (normally). Fun to shoot at the range. Made in America. Kinda cute.