ArmasTermin
Really, self-defense can mean alot.
Personal defense is protecting your person.
Home defense is protecting your home and everything in it.
Self defense can occur anywhere, so I didn't limit size to what you can carry concealed. However, what you can carry concealed depends on what you're wearing. A lithe young woman in a halter top and a mini skirt might be able to stick a derringer somewhere, but a 200 pound man in a heavy jacket and slacks can tuck a full-sized 1911 into a shoulder holster and a revolver at each ankle.
My dad's 6'6" and 350, and he can hide Glock 23 very well. I'm sure if he tried, he could CCW a DEagle well enough to pass cursory glances. Me? I'd need something really small. I can't even hide my mom's Star PD. Gotta try a Walther PPS some day.