An Adam Hunt bodyguard uses a Beretta 92FS in "Pilot". It was never fired. Unidac Industries security guards are armed with the 92FS in "Darkness on the Edge of Town". Mister Blank (J. August Richards) uses a suppressed Beretta 93R, which is most likely a mocked up Berreta 92FS.
Beretta 92FS Inox
The Dodger (James Callis) uses an Inox after he disarms a loanshark's bodyguards in "Dodger". Dominic Alonzo (Ray Galleti) uses one to hold Felicity at gunpoint in "The Undertaking".
Beretta 92A1
Uniformed Starling City police officers use the Beretta 92A1 as their main sidearm.
Beretta Px4 Storm Sub-Compact
A Beretta Px4 Storm Sub-Compact is used by Helena Bertenelli, aka Huntress, in "Muse of Fire" and "Vendetta".
Browning High-Power
A couple of Browning High-Powers were used by bodyguards working for an art dealer in "Dodger".
Crossman 2240 CO2 Pistol
Masked kidnappers use Crossman 2240 CO2s modified to fire tranquilizer darts in "Pilot".
CZ 75 P-07 Duty
A Starling City police officer uses a CZ 75 P-07 Duty pistol when engaging armed gunmen in "Dodger".
Glock 17
Glock 17s are visible throughout the season. This serves as John Diggle's main sidearm throughout the season.
Glock 17 (Full Auto)
An Adam Hunt bodyguard appears to use the full automatic Glock 17 in "Pilot".
Tommy Merlyn (Collin Donnel) uses Malcolm's Glock 26, which has a stainless steel slide, in "Dead to Rights".
Glock pistol (Unknown Type)
Mr. Robbins (Paul Lazenby) attempts to draw out his Glock pistol after he spots something wrong with the express service employee at the front door of the Queen Estate in "Home Invasion".
IMI Jericho 941
Deadshot uses a stainless steel Jericho 941 fitted with a suppressor alongside a Glock 17 in "Home Invasion".
M1911A1
A few M1911A1 are seen in "The Odyssey". Wilson starts using dual M1911A1s in "The Huntress Returns".
Ruger KP89
A Ruger KP89 is used by a hired assassin in "Damaged" with a mounted suppressor.
SIG-Sauer P226
Detective Quentin Lance (Paul Blackthorne), Lucas Hilton (Roger Cross), as well as plainclothed officers use SIG-Sauer P226s as their main sidearm. What appear to be P226s are hurled to the ground by Arrow in "Lone Gunmen" after taking them from security guards. Huntress uses one taken from a Triad gangster in "Vendetta". Triad gangsters disguised as waiters use P226s in "Dead to Rights". Tommy takes a P226 from a dead Emergency Services Unit officer in "Sacrifice".
SIG-Sauer P228
The SIG-Sauer P228 is the main sidearm of all Blackhawk Squad Protection Group contractors. Diggle acquires a P228 from a dead BSPG contractor in "Trust, But Verify".
Leo Mueller uses a stainless Walther P99 in "Damaged".
Revolvers
Ruger SP101
Robert Queen (Jamey Sheridan) uses a Ruger SP101 to commit suicide in order to help Oliver survive with the remaining emergency supplies in "Pilot". Robert shows Oliver that one more bullet is left in the SP101's chamber in "Legacies".
Smith & Wesson Model 10
A Smith & Wesson Model 10 was used by a Vertigo addict after he disarmed a Starling City Aquarium security guard in "Unfinished Business".
Smith & Wesson Model 66
A Smith & Wesson Model 66 is handled by Thea Queen and Roy Harper (Colton Haynes) in "Salvation".
Unknown
Submachine Guns
Beretta M12
A Beretta M12 is used by an underground casino guard in "The Undertaking".
Cobray M11/9
A masked kidnapper was armed with a Cobray M11/9 in "Pilot". What appears to be a M11/9 is used by a Beretelli estate bodyguard in "Vendetta".
Heckler & Koch MP5A3
Starling City SWAT operators use Heckler & Koch MP5A3s as their main submachine gun. It has a railed handguard, vertical foregrip and UMP-based stock, which is the same weapon used in Human Target when it was filmed in Vancouver.
Heckler & Koch MP5K
A rogue Blackhawk Squad Protection Group contractor is armed with a Heckler & Koch MP5K as a backup to the Milkor MGL Mk 1L in "Trust, But Verify". Slade Wilson opens fire on Fyers and his mercenaries in "Salvation" with an MP5K. Thugs guarding Walter's hideout are armed with MP5Ks in "The Undertaking".
Heckler & Koch MP5K-PDW
Somers henchmen use Heckler & Koch MP5K-PDWs in "Honor thy Father". Leo Mueller's henchmen use MP5Ks in "Damaged".
Heckler & Koch MP7A1
Bodyguards working for Adam Hunt use Heckler & Koch MP7A1s to prepare for Arrow's arrival in "Pilot". Leo Mueller's henchmen use MP7A1s in "Damaged". Vertigo's henchmen use them in "Vertigo". Triad gangsters under China use the MP7A1 as seen in "Dead to Rights". A gunman uses one against Arrow in "Unfinished Business".
Uzi
Cyrus Vanch's henchmen are armed with Uzis in "Betrayal".
Micro Uzi
An underground casino dealer fire an Micro Uzi at Arrow during a raid in "The Undertaking".
Jian She Type-05
Triad gunmen use Type-05 as their main submachine gun, first used during the attempted assassination of Laurel Lance in "Honor thy Father".
Unknown
Assault Rifles
AK rifle
An AK-74 is used by an armed mercenary in "Lone Gunmen". The curvature of the magazine suggests that it is 5.45x39mm mag, making it an Ak-74.
AK-47
Some of the mercenaries are armed with AK-47s, first seen in "Damaged".
AKS-47
A few armed mercenaries wield AKS-47s in "The Odyssey".
AKS-74U
Ace, aka Kyle Reston (Kyle Schmid) uses an AKS-74U with a black bakelite magazine in "Legacies".
Colt M4A1
Some of the rogue BSPG contractors are armed with Colt M4A1 outfitted with vertical foregrips, red dot scopes and tactical lights in "Trust, But Verify". A similar configuration is seen in the hands of Starling City SWAT officers in "The Huntress Returns". Emergency Services Unit officers are armed with M4A1s in "Sacrifice".
Enfield L85A2
A mercenary uses an L85A2 in Lian Yu in "Lone Gunmen". A few more are seen starting from "The Odyssey".
Masked kidnappers use suppressed IMI Galil ARs with removed stocks in "Pilot".
Norinco QBZ-97
Yao Fei carries a Norinco QBZ-97 slung on his back in "Vertigo". A few mercenaries are seen with the QBZ-97 in "The Odyssey".
Norinco QBZ-97B
A Norinco QBZ-97B is used by a mercenary hunting for Oliver in "Lone Gunmen".
Norinco Type 56
A few Norinco Type 56 assault rifles are seen at the end of "Home Invasion".
Zastava M70B1
A Zastava M70B1 is used by the Royal Flush Gang, except for Ace, as their main assault rifle in "Legacies". One is used by a few mercenaries in "Burned" and in "Trust, But Verify". Another is seen in "The Huntress Returns". Wilson takes one from a disarmed mercenary in "Sacrifice".
Shotguns
Franchi SPAS-12
A Vanch henchman is armed with a Franchi SPAS-12 when he ambushes Arrow in "Betrayal". A mercenary in "The Odyssey" is armed with the SPAS-12 as well.
Winchester Model 1300
A Winchester Model 1300 fitted with a pistol grip and magazine tube extension is used by Laurel Lance (Katie Cassidy) as a self-defense weapon when Mr. Blank attacks her apartment in "Home Invasion".
Mossberg 500 Homeland Defender
A Mossberg 500 Homeland Defender was used by the Huntress, taken from a disarmed US Marshal in "The Huntress Returns".
Mossberg 590A1
A Starling City SWAT operator is armed with a Mossberg 590A1 in "Pilot". It has a M4-based stock, a saddle shell holster and picatinny railings at the foregrip. The same weapon was used in "Legacies".
Remington 870 Slug Gun
A bank security guard opens fire with the Remington 870 Slug Gun after Derek Reston is shot in "Legacies".
Sniper Rifles
AR-15 DMR
What appears to be an AR-15-based DMR is seen next to the corpse of a Starling City SWAT sniper in "Lone Gunmen"
Springfield Armory M1A
A Springfield Armory M1A outfitted with a riflescope, picatinny railing, riflescope, a laser sight and a JACE-100 stock is used by Deadshot (Michael Rowe), which was first seen in "Lone Gunmen." It's the same weapon used by Guerrero in Human Target.
Remington Model 700
A suppressed Remington Model 700 in a Choate Super Sniper stock by Wilson as one of his main weapons next to his machete, first seen in "The Odyssey".
Machine Guns
Browning M2
A Browning M2 is seen mounted on the Iltis Jeeps used by the mercenaries, first seen in "Damaged". It's also seen mounted on a Humvee, first seen in "The Odyssey".
Daewoo K3 Paratrooper
Some Daewoo K3 Paratroopers (modified with RIS and newer M249 collapsible stocks) were sold by Leo Mueller in "Damaged" to gangster before Diggle (disguised as Arrow) and Oliver (being the real Arrow) broke the arms deal twice. The weapons are actually described in the dialogue as "M249 Squad Automatic Weapons", but they are actually K3s standing in for the M249, which is common in productions filmed in British Columbia.
Grenade Launchers
Milkor Mk 1L
Used by rogue BSPG contractors in robbing armored trucks in "Trust, But Verify" by loading up with tear gas rounds. Diggle is forced to use one in the same episode by attacking a civilian truck before he turns on the contractors by using the Mk 1L against them.
Spike's Tactical Havoc Launcher
Deadshot (Michael Rowe) uses a Spike's Tactical Havoc Launcher with a 9" barrel mounted in a standalone "Kaos" stock system in "Dead to Rights" (S01E16). Rather redundantly, he has another Havoc launcher mounted on the bottom rail of his custom Springfield Armory M1A, but this is never used.
A standalone version of the Havoc was used by Deadshot to blow a hole through bulletproof glass of Malcolm Merlyn's office penthouse in "Dead to Rights".
Others
Bow and Arrow
Oliver uses it during his time in Lian Yu and in Starling City after becoming "Arrow". He uses it as a projectile and melee weapon. Yao Fei also uses it as his weapon in Lian Yu. Malcolm Merlyn in his "Dark Archer" identity also uses one.
Crossbow Pistol
The main weapon of Helena Bertenelli aka Huntress, first seen in "Vendetta".
Wrist Gun
Used by hired mercenary/assassin Deadshot as his main weapon in "Lone Gunmen".
Unknown Mine
Oliver accidentally steps on a landmine in a flashback in "The Odyssey". According to Wilson, the mine's age appears to be dated back from World War II.