Glock (probably a G17)
Caliber: 9x19mm
Capacity: 17
Developed in the 1980s by Austrian engineer, Gaston Glock, the eponymous pistol soon became the world's most popular civilian and law enforcement sidearm. With its polymer frame and simple, internal striker-fired mechanism, the Glock is both lightweight and extremely durable.
Desert Eagle
Caliber: .357 Magnum, .44 Magnum, or .50 AE
Capacity: 9, 8, or 7
In 1979, Magnum Research Inc. set out to create the first gas-operated, magnum-caliber pistol. While the end product is generally considered too heavy and too expensive to serve as a practical combat pistol, it hasn't stopped the Desert Eagle from becoming the weapon of choice for Hollywood (and video game) bad guys.
Micro Uzi
Caliber: 9x19mm
Capacity: 20
The smallest member of the Uzi family was introduced by Israel Military Industries in 1986 as a security weapon to fill the firepower gap between pistols and standard submachine guns. Between its short barrel and extreme rate of fire, things like aiming are but an afterthought.
MP5 N(A3)
Caliber: 9x19mm
Capacity: 30
http://media.gtanet.com/images/3348_gtaiv_niko_bellic_heckler.jpg
The Heckler & Koch MP5 was originally developed in the 1960s, but has been further refined and revised over the years into a number of different models. Thanks in large part due to the number of options available, reliability, and accuracy, it is the most widely used submachine gun today.SW
MP-10
Caliber: 9x19mm Capacity: 30
The Special Weapons MP-10 (also known as the PXP-10) is essentially an MP5 clone with a custom polymer upper. Not much is really known about it, as it's apparently made in very small numbers by a very small and, err, mysterious company. At this point, it's hard to say whether this appears in the game in addition to the MP5 above, or if the MP5 has been replaced since the older screens..
M4 Carbine
Caliber: 5.56x45mm NATO
Capacity: 30
Despite some teething problems with the earlier M16 variant during the Vietnam War, Eugene Stoner's 1958 AR-15 design went on to become one of the most popular and versatile rifles in the world. Boasting a light weight, compact size, and a ridiculous amount of add-ons and accessories, the M4 has something for everyone