The AK might be a good 'assault rifle' in the modern world of 'spray&pray' tactics, but back when the rifleman owned the battlefield with aimed fire, the Mauser 98 reigned as the supreme example of the 'battle rifle'.
I hate to say it, BigDog, but I think cycling speed is a key factor in a battle rifle.
In that sense the Mauser isn't so impressive, especially when providing cover for advancing men.
Used in some form by virtually all armies (except the Brits, Russians, french and a few other small nations), including the USA (the '03) and Japan (the Arisaka).
I believe there were more than a few countries using non-Mausers and the I believe the USA actually used more M17s in WW1 than the Springfield 1903 rifle.
Actually, more than half the Soldiers in the field during WWII were using non-Mausers, arguably because they were using semi-autos.
If you mean world wide then it's still debatable.
The one gun that really shouldn't be listed is the M1 Carbine - not a battle rifle at all.
I think a few vets might disagree.
BTW, I own an Enfield and a Mauser and aspire to own more of both. :wink: