In my humble opinion, there are only four useful handgun cartridges:
1. The .22 Long Rifle. Everyone needs a .22 pistol (they should probably be issued at birth.)
2. The .357 Magnum (and the .38 Special as a subset.) Good for small game with light .38 special loadings, good for a "pocket pistol" in .38 or .357, good for serious self-defense, good for game up to whitetail deer, and good for all around shooting.
3. The .45 ACP. Unbeatable as a self-defense round, especially in it's flagship platform, the M1911.
4. The .45 Colt -- like the .357/.38 a highly flexible round for one who handloads, and suitable for any game on this continent.