The most common classification types of guns by game sides

United States of America and NATO guns:
M-series assault rifles (M16, M4A1), FN SCAR L (H);
M-sniper guns rifles M14 and M24
heavy sniper guns Barret M82A1,
pistols Beretta and Colt 1911;
machine guns M249, Mk 46.

Germany:

G-series assault rifles (G3, G36 and modifications).
G-series sniper rifle G3A
heavy sniper guns Barret M82A1;
Heckler and Koch pistol;
sub-machine guns HK MP7 and HK UMP, and MP5 (modification),
machine guns HK MG 3, 4.

Russia and USSR:
AK Series assault rifles (AK, AKM, AK-74, 100-series, AK-12), AN-94, AEK-971;
sniper rifles: SVD, Val, VSS Vintorez;
pistols: PM, PYA “Grach”;
sub-machine guns: PP-19 “Bison”, MP5N;
machine guns RPK, PKM and PKP “Pecheneg”.

China:
Type-series ( Chinese modification of the AK series) assault rifles (Type95/97/03) ;
sniper rifles SVD and M99;
Type-series pistols ;
sub-machine gun NR08.

https://en.wikipedia.org/wiki/Airsoft_gun