Seen in the hands of Panther and his friends some 20 minutes into the movie. Jackie Chan, with his moves, disarmed someone with it and gave it to Panther, who used it to kill a man who sold him out.
Seen during the boat scene when Jackie was escaping from the police. And one during the last scene where Jackie holds Chaibat's wife at gunpoint.
Smith & Wesson Model 10HB
This looks to be a S&W Model 10HB (heavy barrel) revolver with a different front sight or a 'shaved down' front sight - .38 Special in the hands of Panther.
Submachine guns
Heckler & Koch MP5A3
Seen used by the Royal Hong Kong Police
While the others are A3s, this is an A5. It has four firing modes. - Gunmaster45
Calico M960
Seen in the hands of Panther and one of the General's men.
Micro Uzi
Used by Jessica Yang (Michelle Yeoh) which she took from a drug dealer, Jackie Chan, and Chaibat who took it from Jackie.
PPS-43
Seen in the hands of prison guards. Will try to get some better shots.
Rifles
SKS
In the hand of Chinese prison guards and a scoped one used by Jessica Yang (Michelle Yeoh)
SA80/L85
Seen slung behind an HK police, but without any sights or magazine.
Colt Model 733
Seen with 90 rounds snail drum in the hands of (Jackie Chan)
M16A1
Used by the soldiers of the General and in the hands of one of Chaibat's men that was fitted with an M203.
This is a Cobray 37mm Launcher.
Shotguns
USAS-12
Used by one of the drug lords during the shootout at the base between Thailand and Cambodia
Heavy Weapons
M72 LAW
Used by several of Chaibat's gang during the base assault.
Browning M2
Seeen in the South Asian base, and one was used by Jackie
M203
Seen attached to an M16 used by one of Chaibat's men.
Unknowns
Unknown Revolvers
Seen during the boat scene when Jackie was escaping from the police. And one during the last scene where Jackie holds Chaibat's wife at gunpoint
Unknown Rocket Launcher
Used by one of Chaibat's gang member during the base assault.
Unknown handgun
Seen in the hand of Chaibat's guard when he wanted to test Jackie's loyalty.
Unknown gun
Seen in the hands of Jessica Yang
Unknown SMGs
Seen in the hands of other drug dealers
The one on the left is a Jatamatic SMG. Not sure about the right one. - Gunmaster45
unknown handgun
In the hands of Chaibat in the last part of the movie
Unknown Machine gun
On top of a Malayasian police van
From this angle it looks like a FN MAG58 or the more modern equivalent the M240G. Probably the MAG 58.