Chudnofsky (Christoph Waltz) carries a handgun with twin Desert Eagle-style slides and barrels. It would most likely be impossible to make a remotely useful weapon which worked like the one shown (issues such as how the rounds would feed and eject from the guns are just a few of the problems); even in the movie, Chudnofsky mentions when confronting Danny "Crystal" Clear (James Franco) that the gun was "very difficult 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, something not possible at all in any practical weapon).
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".
Variants of the M1911A1 are carried by several characters.
Submachine Guns
TDI Vector
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.
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 the 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.