.30/06. After 93 years, still the single most useful cartridge for all North American hunting, not to mention whitetails. Today's '06 is a far cry from the same round a generation ago. New powders and better bullets have brought it very close to .300 Winchester Magnum levels of performance. It comes in loadings from 110 grains to 220, but the most useful are the 150 and 165. An experienced handloader can really make the '06 sizzle.