Double-Barreled Handgun (Desert Eagle and Beretta 92FS)
Chudnofsky (Christoph Waltz) carries a handgun with twin Desert Eagle-style slides and barrels. While this appears to be mechanically impossible, Chudnofsky does mention when confronting Danny "Crystal" Clear (James Franco) that the gun was "very hard to make". It appears that the double barreled mockup was built around a modified Beretta 92FS. This was presumably done to show muzzle flashes coming from the gun (and presumably to cut down on costly CGI shots). The handgun is also seen being able to swivel out (presumably for a wider range of fire).
Beretta 92FS Inox
Danny "Crystal" Clear's henchmen are briefly seen drawing Beretta 92FS Inox handguns.
Ruger SR9
A Ruger SR9 is briefly pulled by Danny "Crystal" Clear (James Franco) when confronted by Chudnofsky.
Heckler & Koch USP Compact
Kato (Jay Chou) carries a Heckler & Koch USP Compact as his sidearm. He is first seen using to test out the reinflatable tires of the "Black Beauty".
A TDI Vector is seen held by one of the henchmen during the shootout in the lobby of the Los Angeles Sentinel newspaper. This is one of the first appearances of the Vector in a feature film (it had been previously featured in the series CSI: NY).
Heckler & Koch MP5K-PDW
Another gang member is armed with a Heckler & Koch MP5K-PDW during the shootout at the restaurant.
Another gang member is armed with a Steyr SPP during the shootout at the Sentinel.
Brügger & Thomet MP-9
A Brügger & Thomet MP-9 submachine gun is also used during the shootout at the Sentinel.
Mini Uzi
Another gang member is armed with a Mini Uzi during the shootout at the restaurant.
Machine Guns
M60
When the Green Hornet goes on his crimefighting crusade, an M60 is seen mounted in a gang's van.
Dillon Aero M134 minigun
One of Chudnofsky's henchmen opens fire on the Black Beauty with an SUV-mounted Dillon Aero M134 minigun.
M240 Machine Gun
A truck mounted M240 machine gun is briefly seen when Chudnofsky's men are in front of the Los Angeles Sentinel.
Other
AT4
One of Chudnofsky's thugs is armed with an AT4 during the shooting at the Sentinel.
Gas Gun
The Green Hornet's primary armament is a handheld gas gun.
Kato's Hidden Gun Cache
In a deleted scene, Kato reveals a hidden gun cache to Britt Reid (Seth Rogen), aka "The Green Hornet". Among the weapons is an MP7, an MP5SD, an HK416, a P90, a TEC-9, an AKMSU, and a G36. Plus 2 possible SIG-Sauer handguns, and a UMP.40 or .45 above the HK416 and what appears to be a shotgun standing vertical. Along with a vertical M16 variant.
1 more, a Micro Uzi above th handguns.
Armaments of "The Black Beauty"
The Green Hornet's signature Imperial Crown sedan, known as "The Black Beauty", is fitted with several weapons.
Browning M1919A4
Visually modified Browning M1919A4's are mounted in the front and one is seen mounted in the rear.
Flamethrower
A custom flamethrower is mounted in the grill.
Beanbag launchers
Several launchers that fire non-lethal beanbag rounds are mounted in the grill.
Rocket Launchers
Eight rocket launchers are mounted underneath the grill.