A .303 British Lee Speed with engraving of a red stag suits Australia and NZ well. A kangaroo of course as well. The .303 or its derivatives has probably killed as many kangaroos as any other cartridge.

More exotic, I like the idea of Indian game. Water buffalo, gaur, tiger. Especially the deer species which are in common, India and Australia, sambar deer, chital of axis deer and hog deer.

If it was mine I would strongly have a preference for water buffalo, tiger and sambar deer. If it was desired to have a common Aussie and Indian theme, water buffalo and sambar deer.

As for Africa, maybe a Maneaters of Tsavo theme. With maned lion and perhaps a suitable antelope theme.

On a completely different note, perhaps an Afghan theme, Mujaheddin and Speztnaz Russian soldiers!