MP5

Information
Most used by Minigun users, The MP5 is a sub machine gun secondary able to mow down hordes of zombies in one single clip.

Wikipedia Information
The Heckler & Koch MP5 (from German: Maschinenpistole 5, "machine pistol model 5") is a 9mm submachine gun of German design, developed in the 1960s by a team of engineers from the German small arms manufacturer Heckler & Koch GmbH (H&K) of Oberndorf am Neckar. There are over 100 variants of the MP5, including a semi-automatic version. The MP5 is one of the most widely used submachine guns in the world, having been adopted by 40 nations and numerous military, law enforcement, intelligence, and security organizations. It is widely used by SWAT teams in North America. In the 1990s, Heckler & Koch developed the Heckler & Koch UMP, the MP5's successor; both are available as of 2014.