The Chicago Chopper is a drum-fed Military Spec submachine gun sold at Wizard Island from Trust level 2. It has the highest fire rate and a 55-round drum. It is a primary-slot answer to Freaker crowds at close range.
It sprays down Swarmer packs and smaller Hordes while you back away. Low stopping power means Breakers and Reachers keep coming. Aim for heads to get the most from each drum.
The IDF Pup is more accurate and comes free from Horde Killer. The PPSh-41 is cheaper and also at Wizard Island, but hits softer. The Chopper wins on ammo per magazine.
Buy the extended drum at Trust level 3 before you take on the big southern Hordes. Iron Grip cuts recoil, which keeps the drum on target.
.50 BFG
The .50 BFG is a Special Forces sniper rifle sold at Wizard Island from Trust level 2. It hits harder than almost anything in the game and holds 10 rounds. Bring it for Reachers, Ragers and anything you want dead in one shot.
Eliminator
The Eliminator is a Military Spec heavy pistol that can drop a Freaker in one shot. Jacob D'Angelo sells it at Wizard Island from Trust level 2. Expect heavy recoil and 9 rounds a magazine.
Frag Grenade
The Frag Grenade is a military fragmentation grenade you cannot craft. Hot Springs, Lost Lake and Wizard Island sell them from Trust level 3. Use them on human groups behind cover and on tight Freaker packs.
Lil' Stubby
Lil' Stubby is a sawn-off lever-action shotgun that fits the sidearm slot. It comes in three grades, Poor, Better and Pristine, each sold at a different camp. As a sidearm, you can fire it from the bike.