The Beretta 92FS is seen with various characters in the season.
Colt M1911A1
The Colt M1911A1 is the main sidearm of Conklin (Ryan Robbins) and Baron Reiter (Jimmy Akingbola), as well as his mercenaries in Lian Yu in the season. Taiana (Elysia Rotaru) is seen using it after she and Oliver take the idol in "Lost in the Flood".
Glock 17
The Glock 17 returns in the season in the hands of various characters.
IMI Desert Eagle
The IMI Desert Eagle is used Murmur (Adrian Glynn McMorran) in "Monumental Point" after Darkh breaks him out of prison.
Smith & Wesson Model 3913 LS "Ladysmith"
A Smith & Wesson Model 3913 LS "Ladysmith" is used by Thea Queen (Willa Holland) while under the influence of "yellow pills" given to her by Malcolm in "Lost in the Flood".
SIG-Sauer P226
The SIG-Sauer P226 is used by Captain Quentin Lance as his main sidearm in the season. A P226 was used by Liza Victoria Warner (Rutina Wesley) as her sidearm throughout "Beyond Redemption". Kord Industries guards are armed with the P226 in "Haunted". Andy Diggle (Eugene Byrd) and John Diggle (David Ramsey) uses a P226 as his sidearm in "Genesis".
SIG-Sauer P226R
A SIG-Sauer P226R was used by Lyla Michaels (Audrey Marie Anderson) in "AWOL" when rogue Shadowspire commandos breach ARGUS headquarters. Captain Lance appears to transition to the P226R from "Code of Silence".
SIG-Sauer P228
The SIG-Sauer P228 is used by Lyla Diggle as her main sidearm in "Genesis".
Taurus PT911
A Taurus PT911 was used by Laurel Lance in "Haunted" during a sting. A PT911 is also used in "Canary Cry" by a Black Canary impersonator named Evelyn Sharp (Madison McLaughlin).
Taurus PT92AFS
Danny Brickwell (Vinnie Jones) uses the Taurus PT92AFS from the 3rd season after Darkh breaks him out of prison in "Monumental Point".
Revolvers
Ruger GP100
The Ruger GP100 is seen with Robert Queen (Jamey Sheridan) in archive footage in "Genesis".
Submachine Guns
Heckler & Koch MP5A3
A Heckler & Koch MP5A3 is used briefly by Felicity Smoak (Emily Bett Rickards) near the end of "Restoration" to harass Jeremy Tell aka Double Down when he attacks her. Several are seen in the armories of Oliver and the rogue SCPD SWAT officers in "Beyond Redemption". ARGUS security forces use it as their main weapon in "Monumental Point".
Heckler & Koch MP7A1
The Heckler & Koch MP7A1 is used by Mina Fayed's bodyguards in "Restoration".
SITES Spectre M4
Several SITES Spectre M4s are used by drug smugglers at the start of "Beyond Redemption". Suppressed M4s are used by mercenaries recruited by The Calculator in "Unchained".
Shotguns
Winchester Model 1200
What appears to be a Winchester Model 1200 is used by Noah Kuttler aka The Calculator (Tom Amandes) throughout "Monumental Point".
Assault Rifles
AK-74M
The AK-74M is seen with some of Baron Reiter's mercenaries in the season. It's briefly seen with rogue Shadowspire commandos througout "AWOL".
Colt M4A1
The Colt M4A1 is seen with American law enforcement personnel and with Damien Darkh's Ghost mercenaries in the season. Andy Diggle uses one during his time in Afghanistan in "AWOL".
FN SCAR-L
An FN SCAR-L is seen with some of Baron Reiter's mercenaries in Lian Yu in the season. Oliver uses one while "working" for Reiter.
IWI Galil SAR
A few IWI Galil SARs are seen with some rogue Shadowspire commandos at the start of "AWOL".
IWI Micro Galil
An IWI Micro Galil is used by Conklin as his main assault rifle in Lian Yu in the season.
Norinco QBZ-97
A Norinco QBZ-97 is seen with some of Reiter's mercenaries in Lian Yu in the season.
Norinco Type 56
A Norinco Type 56 without a bayonet attached is used by a Taliban insurgent in a flashback sequence in "AWOL".
SIG SG 552
The SIG SG 552 is used by some of the Baron's mercenaries in Lian Yu.
Sniper Rifles
Juggernaut Tactical Rogue
John Diggle uses an M14 style rifle in a Juggernaut Tactical Rogue chassis fitted with a telescopic sight, suppressor and VLTOR Modpod.
Machine Guns
Auto Turrets
A couple of auto turrets made out of AR-15s with Magpul MOE handguards, G36 carry handles/sights, and with the pistol grips and stocks removed were used in a trap in "Blood Debts".
General Dynamics GAU-17/A
Dual machine guns resembling General Dynamics GAU-17/A are seen on a miniature drone at the start of "Dark Waters".
GE M134 Minigun
A GE M134 Minigun is seen mounted on ARGUS Sikorsky MH-60L choppers at the end of "Schism" in a flashback.
Rocket Launchers
M72 LAW
A M72 LAW is used by Andy during a vehicle chase in the middle of "Genesis".
Norinco Type 69
A Norinco Type 69 is used by a Taliban insurgent in a flashback sequence in "AWOL" (S4E11).
Grenade Launchers
M203A1 Grenade Launcher
A M203A1 grenade launcher is seen mounted under the barrel of a M4A1 used by a Ghost mercenary in "Monumental Point".
A M26 frag grenade is used by Lyla Diggle in "Genesis".
M67 Grenade
A M67 Grenade is used by Oliver in a flashback in "Monumental Point" to take out Reiter.
Others
Bow
The bow used by Oliver back in Lian Yu is first seen in "Green Arrow". Shado is seen using it in a hallucination in "Sins of the Father".
Oneida Eagle Kestrel
The Oneida Eagle Kestrel is used by Oliver when he gets back to Star City and assume the identity of Green Arrow in the season.
PSE Chaos AD
Custom PSE Chaos AD are used by the League of Assassin ninjas from Season 3.
Recurve Bow
The recurve bow, formerly used by Roy, is now used by Thea under the alias of Red Arrow in the season.
Reflex Bow
A reflex bow was used by Carrie Cutter aka Cupid (Amy Gumenick) in "Broken Hearts".
Custom Pistol
Diggle appears to use a custom pistol instead of his Glock 17 as his main sidearm in the season when on the field as "Spartan". Based on "Lost and Flood", it appears to be based on the Blade Runner pistol used in the Blade Runner movie.
Net Launcher
A net launcher was used by rogue SCPD SWAT officers throughout "Beyond Redemption".
Anti-Canary Sonic Gun
An anti-Canary Sonic Gun was used by a rogue SCPD SWAT officer throughout "Beyond Redemption". This weapon is a reused "Bone Jack" prop from Blade: Trinity, a modified Winchester Model 1887 which has appeared in several other Vancouver-produced television shows.
Jing Gong MP5K RIS JG202
Several Jing Gong MP5K RIS JG202 are seen in a baby crib in "Genesis" as a substitute for the actual MP5K.
Armory
Several small arms are seen in the underground hideout of the Green Arrow throughout the season.