I usually carry. Most of the time, it's a little North American Arms revolver in 22 WMR, as it's the least bulky, which means I'm most likely to carry it. Reload time really sucks with this gun, as you have to take the cylinder out to reload it. Also, with its extremely short barrel and sight radius, it's not the most accurate pistol, either. However, I can put 5 shots in the head on a B-27 at 10 yards with it, so, that's good enough for me.
But, if 5 to the dome on one bad guy, or 1 in the dome of 5 bad guys.... doesn't solve the problem, then, I've obviously gotten myself into a real fix, and it's time to go for the truck gun, the SKS side-folder with a chopped down 16" barrel, with a 30 round mag, then an extra 30 rounder, both loaded with Norinco yellow box (steel core) ammo. (And if you think that's heavy firepower for a truck, you should see my house. In every room, there is a weapon stashed, ready to go)
Another favorite carry gun I have is a Colt Mustang Pocketlite in 380. Again, a minimal caliber for self-defense, but the first rule is to have a gun.
The second rule...although not mentioned often enough, is to know how to use that gun with extreme proficiency, including under stress... and make well-placed shots that will incapacitate an attacker. A good stressor is competitive shooting, or, if you feel froggy, get some airsoft or paintball guns and do some force-on-force training with some buddies.
Think airsoft or paintball is for kids? Don't laugh. You'd be surprised how bad the hit ratio drops off in a simulated firefight, even for an experienced marksman....it can drop to as much as a 20% hit ratio for the number of rounds expended.
Paper targets and steel poppers do not fire back. While marksmanship training is a good thing, it still does not replicate the stress level of force-on-force training. If you can get to a point where you can perform with even a 50% hit ratio in a simulated firefight, you've got a better chance of walking away alive from the real thing.
And as for the marksmanship training...try some 100 yard shots with your handgun, with iron sights... (no cheating with scopes or lasers!)
What is the purpose of this, you ask. Simple.
Refer to the 20% hit ratio in a firefight.
OK, this means that if you can hit a 6 inch steel plate at 100 yards with your handgun, not under stress from being shot at.....then, when you factor in that 80% reduction in the hit ratio during a firefight, that means your max effective range drops to 20 yards.
Conversely, some people that carry have trouble holding a group at just 10 yards. What happens when TSHTF? You don't want to be following that guy into a firefight, much less into a dimly lit barn.
Just a little food for thought......