Different strokes, different folks. Different guns, different countries. Here's a map showing the military issue rifle for each country in the world. You'll see familiar M4s, AK-47s, AK-74s, some M16s and tinkles of other weaponry. Judging by the map's choice of colors, it seems to group weapons that are of a similar family together by color.
To be sure, there are more guns used by the military than just these but this map gives a general gist of each military's standardization. Here's a rundown of what some of these guns look like, courtesy of Wikipedia:

M4

What the Military Issue Rifle Is in Each Country of the World

M16

What the Military Issue Rifle Is in Each Country of the World3

AK-47

What the Military Issue Rifle Is in Each Country of the World

AK-74

What the Military Issue Rifle Is in Each Country of the World

QBZ-95

What the Military Issue Rifle Is in Each Country of the World4

Heckler & Koch G36

What the Military Issue Rifle Is in Each Country of the World
You can hit the expand button for a bigger map. Full-sized version of the map can be foundhere.
What the Military Issue Rifle Is in Each Country of the WorldSOURCE

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