|The Samaritan, Hellboy's Handgun|
1. Reliability. The less complex mechanisms of traditional revolvers don't jam nearly so often as automatic pistols.
2. Durability. Fewer moving parts and an all-metal construction means your pistol could still be holding off blood hungry hoards when the sun re-appears. Polymer frames are for short-timers.
3. Flexibility. The .357 Magnum cartridge is based on Smith and Wesson's older .38 Special. While the magnum packs a lot more power, the cases are actually the same diameter and your .357 will happily shoot .38 bullets. That means more potential sources of ammunition. Plus these common calibers should be easier to find than more exotic sizes.
4. Power compromise. .357 sits perfectly in the middle of the power spectrum. You won't break your wrist, but even the largest zombie will be stopped in its stump dragging tracks. If the kid has to guard while you investigate potential food sources, load up .38's for less kick.
5. Weight. More comforting than a .38 without the near tonnage of a Desert Eagle .50 cal. It's a gun that feels good in the hand and bad in the back of your enemy's head after you resort to pistol whipping.
6. Easy to fire. In an emergency, weaker/stupider/less-gun-savvy members of your party should still be able to load and fire a simple six-shooter. If not then, well, I'm sorry. They were never made for this life. It's not your fault.
7. Easy to clean. You're going to get completely filthy wandering around the nuclear-winter-wonderland and so is your gun. From gritty ash to acid rain to unknown substances encountered in the horror of a mutant lair, you better be able to clean your weapon in a jiffy.
8. Speed-loaders. Still think a 9mm automatic with a 12 round clip sounds better? Consider grabbing a few speed loaders, nifty little bullet holders that make for super quick revolver reloading with a little practice and preparation.
9. Style/Intimidation factor. Face it, nothing says "I mean business. I'll kill you if you try to take my water," like brandishing a big f'ing revolver. Plus, their classic style might distract from your terrible radiation burns when courting the opposite sex.
10. Ease of acquisition. We'd all love to have a machine gun oiled and ready for Armageddon, but procuring a reasonably priced revolver prior to judgement day seems much more realistic.