Desert Punk carries a "Riot" length Winchester Model 1897 as his primary weapon. Along with firing standard shotgun ammunition, it is also depicted as being capable of firing more exotic projectiles, such as grenades. Although normally depicted as the takedown frame variant, a solid frame variant appears in the live action opening credits.
Submachine guns
PPSh-41
Several members of the Kawazu Gang carry an PPSh-41s in "The Demon and the Double D's" (Ep01).
Uzi
One of the members of the Kawazu Gang carries an Uzi in "The Demon and the Double D's" (Ep01).
MAC-10
One of the members of the Kawazu Gang carries a MAC-10 in "The Demon and the Double D's" (Ep01).
M1928 Thompson
Several members of the Kawazu Gang carry M1928 Thompsons in "The Demon and the Double D's" (Ep01).
M3
One of the members of the Kawazu Gang carries what appears to be an M3 in "The Demon and the Double D's" (Ep01).
Taiko's mother uses Steyr TMP and other unknown SMG.
Rifles
Colt AR-15 Sporter Carbine
Several members of the Kawazu Gang can be seen with Colt AR-15 Sporter Carbines with barrel mounted flashlights and 20 round magazines in "The Demon and the Double D's" (Ep01).
Armalite AR-7
Armalite AR-7 is seen used during Desert Punk's and Rain Spider's duel with each other.
AK-47
Several members of the Kawazu Gang carry AK-47s in "The Demon and the Double D's" (Ep01). Kanta Mizuno has AK-47, but he didn't use it.
FN FAL
Several members of the Kawazu Gang carry FN FALs in "The Demon and the Double D's" (Ep01). Taiko Koizumi also uses a FAL
Desert Punk acquires a Remington M40A1 sniper rifle in the fourth episode but would later lose it later in the same episode when the Shimmer Sniper puts a bullet through it. It is later repaired and used by Kosuna at various points, notably during Desert Punk's meeting with the Machine Gun Brothers and after Desert Punk's supposed death.
M79
An M79 grenade launcher is carried by Kosuna in several episodes. It also appears in the ending credits.
A modified M1 Carbine is the main weapon of Rain Spider. The M1 Carbine Rain Spider uses has its barrel shortened and its stock removed so the carbine is cut down to pistol size.It is also made out of steel.
Launchers
RPG-7
RPG-7s are used by several members of the Kawazu Gang in "The Demon and the Double D's" (Ep01).
Grenades
M26 Hand Grenade
M26 hand grenade is seen used during Desert Punk's and Rain Spider's duel with each other..