The Glock 17 is not a user-selectable weapon in the released game. It is used by enemy terrorists exclusively.
M1911
The M1911 is available with or without a suppressor in both .45 ACP and 10mm Auto as the 1911 and "1911 Elite"; both use the same models.
Beretta 90Two
As with the 1911, the Beretta 90Two is available with or without a suppressor, and in either 9mm or .40 caliber with visually-identical models, misidentified as the 92FS and 96FS respectively.
Submachine Guns
Heckler & Koch MP5A3
The Heckler & Koch MP5A3 appears as the "M5 SMG", fitted with a UMP-style folding stock, RIS handguard with a flashlight and vertical foregrip.
Heckler & Koch MP5SD3
The Heckler & Koch MP5SD3 appears as the "M5SD SMG"; like the MP5A3, it is fitted with a UMP-style folding stock, flashlight and vertical foregrip. It can only load subsonic ammo, most likely to simulate that the MP5SD's barrel is ported to bleed off velocity, rendering supersonic ammo subsonic.
Heckler & Koch MP5K
The Heckler & Koch MP5K is the third MP5 variation, appearing as the "M5K PDW". Unlike the others, it is overall unmodified from its real-world appearance.
Colt 9mm Submachine Gun (R0991)
Much like the sidearms, the Colt 9mm Submachine Gun is available in two visually-identical variations, the "CQBP-9" and a fictional "CQBP-40" that is, as its name indicates, chambered for .40 S&W.
Steyr AUG A3 9mm XS
The Steyr AUG A3 9mm XS was added alongside the full-sized AUG variants in a February 2014 patch, appearing in-game as the "AG-3P SMG". Like the other variants, it includes the original folding foregrip alongside a rail above the receiver.
Assault Rifles
AR-15
In addition to the Colt SMG's, there are AR-15 variants with barrel lengths from 7.5" to 18" in 5.56x45mm, .300BLK, 6.8x43 SOCOM, 7.62x51mm and .458 SOCOM. All variants are select-fire and have a permanently attached flashlight.
Colt M4A1
Among the AR-15 variants is a Colt M4A1 carbine, available in the original 5.56mm.
Armalite AR-10 A4C
18" AR-10 with Magpul MOE-esque handguard and standard M4 style buttstock. Available in both 7.62x51mm, as well as a variant in 6.8x43mm SOCOM which, despite that cartridge being based on 5.56mm NATO, uses the exact same base model.
AKM
The AKM is the first non-AR-based assault rifle available. Unable to mount any attachments. Counter to stereotypes, it has accuracy on par with the AR-15 variants.
AK-74M
The AK-74M is also available, identified as simply the AK-74. Like the AKM, it cannot mount any attachments.
AK-103
The AK-103 appears as the "SA-47T", with an AR buttstock, RIS handguard, flashlight and vertical foregrip. Unlike the other AK variants it is able to mount all attachments, but in return it has the AK's stereotypical terrible accuracy.
Might be a heavily customized AKM.
Steyr AUG A3
The Steyr AUG A3 was added in a February 2014 patch. Available with both the standard-length barrel as the "AG-A3 Carbine", or a long-barreled variant meant for sniping as the "AG-DMR". Both variants have the full rail cluster and the original AUG folding foregrip.
Shotguns
Saiga 12K
The Saiga 12K appears as the "SA-12 Shotgun" with a folding AR-style stock, custom flash suppressor and permanently attached flashlight.