I've got an article xerox'd out of an old Gun Digest describing methods for making better shotshells for handguns than you can buy. The idea was to build brass cases that went the full length of the handgun's chamber, thereby increasing the shot charge.
I made some .45 Colt loads out of 444 Marlin brass according to the recipe, and they were damn good shot loads. I used #9 shot and they patterned well out to 10 yards, good enough for rats, snakes, etc. If I wanted to use 'em on bigger varmints, I suppose I could load them up with #6 shot, but you're really starting to reduce pattern density at this point.
In .44's, you've got to get a bit more technical with the brass--I can't remember off hand what brass you have to use, but it requires shaving the rim down as well as shortening the rifle cases...40 Krag? .... I can't remember. I wouldn't bother building shotshells for anything smaller than a .44, though. The cases are just too small.
I've heard that the CCI shotshell in .45 ACP is decent for snakes in close. Haven't tried it, myself.