Walt's seen my smallest: a Freedom Arms .22Magnum minirevolver, 4shot, 1.5" barrel and grips the same size as an NAA .22LR minirevolver. It's *small*, absolutely and totally discrete.
He also saw me drop all four onto a 4"x6" steel plate at around five healthy paces, firing one shot per second. This one's marked "Casull's Improvement" and is about 10 years old, it pre-dates FA selling the minirevolver biz to NAA.
I paid $140 total for that little beast, made my own pocket holster for it. It's a "deep cover front-pocket surprise"...any mugger wants my wallet, he's gonna get a 30grain JHP doing 1,200FPS in the face.
I've also got a 4" bull-barrel NAA Mini Master with a trigger job in dual .22LR/.22Mag convertable. THAT discrete little pup can stay within 5" at 25 yards with defense-grade Mag JHPs.
Either of these runts should at least be able to penetrate skull on a headshot...and they're absolutely undetectable on the street. I carry the .22LR cylinder for the 4" loaded with Yellowjackets, in the probably vain hope I could keep their heads down with "Baby" the FA mini while reloading the 4" with a "Clint Eastwood style" cylinder swap.
I also favor .38 snubs...but the two minis put together still add up to less bulk.
Jim March