I had bigger toy guns when I was a kid. However, since the 32 ammo is expensive, I recommend a 22 for minimum recoil. If that sounds lame, remember, a potential assailant is not going be that interested in the caliber of the round the doctor is digging out of his testicles. Besides, the 22 is "round of choice" at close range, because it "bounces around" inside the body and does a lot of damage. For home defense, I prefer a 12 gauge. As long as you hold it properly to your shoulder, the recoil is actually less than most handguns I've fired. Best of all, while it won't penetrate body armor, the concussion will not only disable the target, it will do enough internal damage to kill an intruder with one shot. Moreover, at distances below 20 feet, you virtually cannot miss. Best of all, simply the sound of someone pumping a shotgun will make many an intruder relieve himself in his pants as he runs off.
Oh also, about the 22 Chief's Special; since it has no safety or hammer, I keep an one chamber empty and squeeze it twice in rapid succession to fire it. Since that means you can only load four rounds, I suggest you buy a speed loader for it.