Huang uses a Beretta M1934 as his main sidearm, which is used to wound Hei when he tries to leave the Syndicate. He also uses it to execute Shihoko as part of his orders from Syndicate leaders.
Glock 17
Hired gunmen also use Glock 17s at their main weapon. Kenneth also uses a Glock 17 when he captures Mai Kashiwagi, who was under the influence of Moratorium. Yakuza leader Hitotsubashi carries one as his sidearm.
Heckler & Koch USP
The head of PANDORA's security uses a Heckler & Koch USP as his personal sidearm. Nick later uses this against Hei when he realizes his electricity is nullified by Hei's own powers. The Yakuza also appear to use this firearm.
Smith & Wesson 3913
Misaki uses a Smith & Wesson 3913 as her main sidearm in the series. Hōrai uses this to execute Eric Nishijima after Hei destroys the Saturn system in the PANDORA complex before planting it on his body. In the OVA, she uses it with great efficiency in shooting Hei's knives and the grapple wire used to strangle Saito.
Tokarev TT-33
The Tokarev TT-33 appears in the hands of Mafia members in Eastern Europe.
Norinco Type 54
A Norinco Type 54 is used by a Yakuza gunman.
SIG-Sauer P230
Saito, Kono and DGSE agent Alain use SIG-Sauer P230 pistols as their main sidearm.
Revolvers
Smith & Wesson Model 37
Japanese police officers use the Smith & Wesson Model 37 as their service weapon. This is correct since it's a standard-issued sidearm to any Japanese police officer aside from the New Nambu Model 60.
The Heckler & Koch MP5A3 is seen being used by various Tokyo Metropolitan Police Department police officers/Public Security Bureau detectives, MPD Special Assault Team operators and Japanese-based MI6 agents when higher firepower is required. Meyer & Hilton henchmen also use this when they wait for Hei's arrival.
PANDORA security forces use the Heckler & Koch G11K2 as their main service rifle.
Sniper Rifles
Unknown Sniper Rifle
Huang uses an unknown bolt action sniper rifle to shoot Russian SVR agent Itzhak as he attempts to escape from Hei before he tried to assassinate Yin as ordered by the Syndicate. Based on the small chamber and bolt size, it appears that the artist used a bolt-action .22 rifle (such as a Marlin 925) for the design.
Machine Guns
Sumitomo NTK-62
PANDORA security forces fire Sumitomo Type 62 machine gun mounted on top of their Type 96 APC against Evening Primrose contractors.
Grenades
Sleep Gas Grenade
Huang uses a sleep gas grenade to disorient Misaki and the other PSB officers after being ambushed.
Grenade Launchers
Heckler & Koch HK69A1
Huang uses a Heckler & Koch HK69A1 grenade launcher to free Hei and distract November 11. It was also used to ambush Misaki and her PSB team escorting November 11 and his M16 agents.
Rocket Launchers
Pansarskott m/86
PANDORA security forces fire Pansarskott m/86 rocket launchers to destroy cover used by Evening Primrose contractors after the group launches a frontal assault at the complex.