The M4A1 carbine looks like it will be the main weapon for the Tier 1 Operators in the game. They appear to be fitted with suppressors, RIS foregrips, and EOTech red dot sights. Rangers were seen with these as their primary weapons.
M16 variant
A variant of the M16 appears in the recently released multiplayer trailer, firing on full-automatic.
AKM aka AK47
This assault rifle will be seen, as in most modern war video games, in the hands of the enemy of the Tier 1 Operators. It is very briefly seen twice in the world premiere trailer.
AKS-74U
The compact carbine version of the AK-74 can be seen in the MP trailer.
Mk 46 Mod 0
The FN Minimi variant is seen with an Eotech sight.
Mk 14 Mod 0 Enhanced Battle Rifle
A Ranger was seen with this M14 EBR in the new trailer "Leave a Message"
PK machine gun
PKM can be seen in the extended trailer mounted on a technical.
GP-3?
Improvised Explosive Device
IED's detonated via cell phones can be seen in the MP trailer.