An Adam Hunt bodyguard uses a Beretta 92FS in "Pilot". It was never fired.
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, first in "Muse of Fire" and in "Vendetta".
Crossman 2240 CO2 Pistol
Masked kidnappers use Crossman 2240 CO2s modified to fire tranquilizer darts in "Pilot".
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".
Glock 19
A Glock 19 is seen in the hands of Anthony Venza (Alex Zahara) in "Vendetta".
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".
SIG-Sauer P228
The SIG-Sauer P228 is the main sidearm of all Blackhawk Squad Protection Group contractors. Diggle acquires a P228 after picking it up from a dead BSPG contractor in "Trust, But Verify".
Leo Mueller uses a stainless Walther P99 as his sidearm 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".
Unknown
Submachine Guns
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".
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".
IMI Uzi
Henchmen of of Cyrus Vanch is armed with an IMI Uzi in "Betrayal".
Jian She Type-05
Triad gunmen use Jian She Type-05s as their main submachine gun, first used during the attempted assassination of Laurel Lance in "Honor thy Father".
Assault Rifles
AK rifle
An AK-type rifle is used by an armed mercenary in "Lone Gunmen". Not much details are given to show what kind of rifle it is.
AK-47
Some of the armed mercenaries are armed with AK-47s in "Damaged" and in "Vertigo".
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 M4A1s outfitted with vertical foregrips, red dot scopes and tactical lights in "Trust, But Verify".
Enfield L85A2
An armed mercenary uses the L85A2 in Lian Yu in "Lone Gunmen".
Heckler & Koch G36K
An armed mercenary is armed with the Heckler & Koch G36K in "Damaged".
IMI Galil AR
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".
Norinco QBZ-97B
A Norinco QBZ-97B is used by a mercenary hunting for Oliver in "Lone Gunmen".
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".
Shotguns
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".
Unknown
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) in "Lone Gunmen." It's the same weapon used by Guerrero in Human Target.
Machine Guns
Browning M2
A Browning M2 is seen mounted on an Iltis Jeep in "Damaged". Given that the show is produced in Vancouver, the production crew got the Iltis instead of American-made jeeps and Humvees.
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.
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.
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".