So there is a Russian weaponry list... A long, long one, I'm afraid.
Pistols and revolvers:
OTs-38 Stechkin silent revolver - a rare example of silent revolver, utilizing Russian piston cartridges. If we want something original, that's the thing. Well, one of the things, but a nice one.
MP-443 Grach - chambered for increased penetration 9x21mm Russian cartridge. Interesting, but produced in small quantities so far.
SMGs:
Bizon - chambered for 9x18mm, and pretty popular in recent FPS games, it uses helical magazine with 64 cartridges.
PP-2000 - a PDW chambered for good old favourite, 9x19mm, but designed to take advantage of new Russian versions of the cartridge with increased armour piercing capabilities. Also quite interesting looks.
PP-90 and PP-92 - for 9x18 and 9x19mm, respectively, with futuristic looks. Not produced in huge numbers... yet.
SR-2 - chambered for yet another variant of 9mm, the 9x21mm with tungusten core, designed to penetrate low-class bulletproof vests, able to stop ordinary pistol bullets.
PPSh-41 - well, this is really low-end right now, but for the poorest part of Africa, maybe?
Vityaz-SN - pretty standard one, with 9x19mm chambering, but it is now a standard SMG for most branches of Russian military and para-military organizations, which means it should be easy to skim a few.
ARs:
AS Val - also quite rare example of assault rifle with integrated suppressor. Using special 9x39 mm cartridge, it is known and liked by everybody who ever played Stalker.
AN-94 - known as Obokan or Abakan, modern replacement for older AK rifles. Due to problems with costs it will probably never replace AK-74... All the more reason to sell it on the side.
AK-47, AKM and AK-74 - no explanation needed, I think?
AK-107 - currently in testing as another option to replace AK-74.
AEK-971 - one more AR in trials to replace AK-74. Those are all quite similar, so I think it should be enough, even though there are quite a few more.
A-91 - bullpup assault rifle with integrated grenade launcher, currently in use with some elite units in Russia. Much more interesting design.
OTs-14 'Groza' - bullpup AR designed as a replacement for AKS-74U, shorter, carbine variant of AK-74.
SR-3 - yet another version of special-operations focused AR chambered for 9x39 subsonic round. Variant SR-3M with collapsible stock and detachable suppressor can fulfil variety of roles during special operations.
Machine guns:
RPD - older LMGs, served as kind of basis for later SAWs used in Soviets and subsequently in Russia. The production ceased in 1960s, but it is still in widespread use today, as is the case with numerous Soviet designs.
RPK - RPDs younger brother, or maybe more of a son. The RPK-74 version is still in production, and there are probably massive amounts ready to be bought and sold without many questions asked.
PK and newer PKP 'Pecheng' - heavier MGs firing 7.62x54mmR Warsaw - Pact style ammunition, in contrast to lighter 7.62x39mm used by RPD and RPK. Especially PK is used in massive numbers but it is soon to be replaced by Pecheng.
Kord-12.7 mm - as the name suggests, it is even heavier machine gun, currently in production and usage in Russia and for exports.
Sniper rifles:
VSS Vintorez - sister of AS Val, a suppressed sniper rifle using 9x39 mm ammunition. It can be stripped down to fit in standard sized briefcase.
Dragunov - because there are things that just must be included not to disappoint everybody.
SVU - much shorter, bull-pup version of Dragunov.
SV-98 - bolt action sniper rifle with effective range reported to be up to 1000 meters.
OSV-96 - anti-material sniper rifle chambered for 12.7x108mm Russian round, effective up to 1800 meters against enemy infantry and up to 2500m against vehicles. It is perceived as anti-sniper weapon, due to great range.
VKS - 12.7x55mm suppressed sniper rifle designed to engage heavily armoured targets in silence. Quite rare, but I always find it fascinating that there exists a thought process leading to creation a half-inch silent cartridge.
Grenade launchers:
RG-6 - revolver GL with quite unique appearances, firing 40mm caseless grenades.
AGS-17 'Flame' - fully automatic grenade launcher, using 30mm grenades.
AGS-30 - much newer fully automatic grenade launcher, also 30mm grenades.
GP-25 - underslung GL using 40mm caseless grenades.
Shotguns:
Baikal MP-153 - a semi-automatic shotgun. We don't have lot of those on the list so far, I think.
Saiga-12 - also well know, fully automatic, 12-gauge shotgun.
RMB-93 - short shotgun designed to limit encumbrance as much as possible.
Rocket launchers:
AT-13 - two-man portable anti-vehicle missile system. Know from BF3, but it was stationary there.
RPG-7 - older variant, reloadable and pretty well known from a variety of sources.
RPG-26 - much newer, disposable variant of anti-vehicle rocket launcher.
Mortar:
2B14 - 82mm mortar, because a mortar every now and then should be a useful thing. Also, Dogs of War.
So, I think that only USA is left?