The AN-94 was developed in Russia. It has been in service since 1997. It has an effective range of up to 700 meters and it can rattle off 600 rounds per minute. This was one of the assault rifles to make an appearance in the multiplayer reveal trailer. If you remember correctly, this gun was used by the player who was firing at enemies via a hole in his Assault Shield.

M8A1
The M8A1 is based on the XM8 assault rifle, which was developed by Heckler & Koch. It's gas-operated with a rotating bolt and it can fire 750 rounds per minute. In-game, it seems to be a burst-fire / select-fire weapon that shoots 4 rounds per trigger pull. It has low recoil and a reload time of about 3 seconds.

Type 25
Type 25 is an automatic bullpup Assault Rifle. Fun fact: A similar-named weapon also appeared in the Halo series. In-game, it has low recoil and it carries 30 rounds by default.

Scar-H
The H stands for Heavy. In real life, it has been in service since 2009. In previous games, the SCAR-H was a powerful Assault Rifle that had a low rate of fire.

SVU-AS
The SVU-AS is Russian in origin and it's design is mainly based on the Dragunov SVD. Apparently, the "SVU project" began back in the 1970s when the Russian's decided that they wanted a compact sniper rifle for it's airborne division. In-game, it acts as a semi-game. Technical details include "gas operated" and "rotating bolt" design. As you see, it looks pretty lightweight:automatic and it seems to handle just like Dragunov did back in the previous Black Ops.

Ballista
In one piece of footage, a guy was using the Ballista with a red laser beam on it. In real life, it's referred to as the FNH Ballista; a "multi-caliber and modular behemoth" that boasts a "suppressed .338 system".

DSR-50
This particular weapon was developed by DSR-Precision in Germany.

M1216
The M1216 is an automatic shotgun that holds 16 rounds per magazine. After 4 shots have been fired, your character will cycle to the next chamber and continue on firing. It's worth noting that this weapon has appeared in other games before; just not in Call of Duty. This particular weapon was made with a compact design:

R-870 MCS
I've been unable to find any real life information on the R-870 MCS. All I know is that it appeared in the game Combat Arms. In-game, it's a pump-action that has a 8 shell tubular magazine.

LSAT
The LSAT LMG was developed in the USA and Germany after the Joint Service Small Arms Program challenged the defence industry to design lighter guns and ammunition.

QBB-LSW
The QBB-LSW was developed in the People's Republic of China. It has been in services since 1997. It is actually a LMG variant of the Chinese Type 95 family (if you remember correctly, the Type 95 was a burst-fire weapon back in MW3.

Tac-45
In real life, the Tac-45 is called the FNX-45 Tactical Handgun. Developed for U.S. the Joint Combat Pistol Program.

KAP-40
The KAP-40 is a semi-automatic low-recoil handgun that can hold up to 12 rounds in its magazine.

Raging Judge- Known as Magnum
The Raging Judge is huge in real life. Seriously, it's looks like some sort of mini cannon. Developed by a company called Taurus, this magnum / revolver can actually hold the .454 Casull, which means that it can take down almost anything. In-game, it's also referred to as The Executioner. It holds 6 rounds and is a semi-automatic. This actually shares the same sound as the Python from the original Black Ops game.