Drebin

Drebin is an Arms Dealer who is currently working in the middle east. It is unknown why he is located in the middle east, it appears to help the underdog but more likely to make money.

The Arms Dealer
Drebin is a Arms Dealer who can modify, sale, and exchange weapons on the fly that originally belong to the PMC. Along side Drebin is Little Gray, a monkey who wears nothing but a pair of underwear. Together, Drebin and Little Gray sell modified weapons to the underdog country who is currently at war against the Praying Mantis military. Little Grey originally meets Old Snake, but Derbin is stops Old Snake from shooting and tells him that he can get rid of ID tags on the weapons belonging to PMCs and sell them to old Snake along with bits of information.

His Role in MGS4
Besides being a Arms Dealer, he is most likely considered a comic relief character (as shown in the latest trailer). Little Gray apparently drinks what Drebin drinks, and shouts words obnoxiously. He also knows a little bit of magic (as shown in the latest trailer) but it is unknown if he really knows alot of magic tricks.