I think I'll have to go with the 7 x 57 Mauser cartridge....just my favorite personal pick....not sayingit's the best for everything (if there is such a thing)
It is what my first hunting rifle was chambered in....and the first round I learned to load on my single stage press. A darn good versatile round that's also pretty freindly to your shoulder but can get the job done on pleanty of sizable game.