The Guatemalans were using the Galil when I was there in the early 80's. I can tell you that for sure and for certain.
My curiosity being piqued, I did a quick search and found 23 other nations, large and small, who issue the Galil as a standard weapon, or for certain applications.
Are we restricted to guns introduced after 1960 or just guns still in use after 1960? If it's the latter, then my vote is a tossup between the FN-49 and the Stg. 57. If we're restricted to rifles introduced after 1960, then I'll bend the rules a bit and go with the AN-94 (it was the Russian Federation and not the Soviet Union by 1994 and the rifle is standard issue to Spetsnaz).
I thought sure the AUG would lead the pack. Nothing remotely like it, that combined the bull pup, w/ integral optic and trigger driven fire control ( I just made that term up, like it?) especially when it first hit the market.