The IDF Pup is a Special Forces bullpup rifle you get free for clearing Hordes. It unlocks at 50% of Horde Killer with a 45-round magazine. It is accurate, fast and one of the best primaries for Horde fights.
Clear 20 Hordes to unlock it, then 30 for the bigger magazine. It cannot be bought.
It is a Horde weapon first. The high accuracy keeps headshots landing while you back up. It also tears through human camps at mid range.
The Chicago Chopper holds more rounds per drum but costs 3,000 credits. The US556 is the best buyable rifle in the north. The Pup beats both on accuracy.
Auto Shotgun
The Auto Shotgun is a Special Forces drum-fed shotgun you get free from the Horde Killer storyline. It fires shells as fast as you pull the trigger. It is one of the best close-range tools for Freaker crowds and Breakers.
MG55
The MG55 is a Special Forces medium machine gun with very low recoil. It unlocks free at 60% of Horde Killer and goes in the special slot. It is the best machine gun for taking a Horde apart.
SMP9
The SMP9 is an automatic sidearm with a 30-round magazine. You can buy it at Hot Springs or Lost Lake, or get a better Mil-Spec copy free from Horde Killer. Full-auto in the sidearm slot is great on the bike.