The following weapons were used in the OVA Gunsmith Cats:
Rally Vincent carries an early model CZ 75 as her primary weapon of choice. She praises this weapon throughout the manga, considering it to be one of the best handguns ever made, due to the very high grade of steel used to make the first versions of the CZ 75.
Rally keeps a Colt 1908 as a backup weapon. The gun is attached to a special harness that allows the gun to be drawn by flicking her wrist, and has the triggerguard removed. This is an obvious shout-out to Taxi Driver (Kenichi Sonoda, the author of Gunsmith Cats, often cites American action films as a source of inspiration).
ATF agent Bill Collins uses a Walther PPK as his weapon. At one point, Rally makes a joke at Bill calling him "Agent Double Oh 7-11".
Rally uses this gun briefly in the first episode, when gun runners tell her to shoot Bill as a sign of trust. She instead shoots the ropes used to tie him up, hitting one of the gun runners in the leg in the process.
Near the beginning of the first episode, an off-duty cop brings his Beretta 92FS in to Rally's shop to get some custom work done. When checking the gun, Rally notices the weapon still has a round chambered and informs him to be more careful next time.
Another Beretta 92FS appears in the second Episode, when Russian assassin Natasha Radinov attacks an ATF safehouse. She either brought this weapon along or picked it up off a dead ATF agent.
In the third episode, Rally is seen cleaning a disassembled nickel M1911A1.
Colt MK IV Series 70
A Colt MK IV Series 70 is seen on the wall of the Gunsmith Cats shop.
Assassin Natasha Radinov briefly uses a CZ 52 to kill an ATF agent when she attacks the safe house.
Welrod Mark IIA
In the third episode, Radinov uses a rare British bolt action Mark IIA Welrod pistol to kill ATF chief George Black. The weapon exhibits some rather bizarre changes between shots.
Heckler & Koch VP70
In the third episode, Radinov attacks Rally and May at Senator Haints' campaign rally with a Heckler & Koch VP70M. The VP70M has its stock attached, loaded with an extended magazine.
Near the end of the third episode, Senator Haints grabs what appears to be a SIG P226 to shoot Natasha Radinov. The weapon turns out to be empty and part of a set up by Becky and Cathy to get Senator Haints to admit his crimes.
Heckler & Koch USP
A Heckler & Koch USP is shown during the opening credits.
During the third episode, Bill's partner is carrying a Glock 17. One was also seen on the wall of the Gunsmith Cats shop.
A Mauser C96 is seen in the Gunsmith Cats shop and at their home.
Norinco Type 82-2
A Norinco Type 82-2 is used by Natasha when she storms the ATF safehouse.
Smith & Wesson Model 36
A Smith & Wesson Model 36 is shown during the opening credits. Rally also keeps one of these guns under the counter of her store.
Rally keeps a Ruger SP101 taped to the door of her fridge.
A stainless Colt Python with a 8 inch barrel and a scope is shown briefly during the opening credits. The words "Python Hunter" are written on the side. One with a 4 inch barrel is used by Rally at a shooting range.
In the manga series, Roy Coleman mentions he carries a Colt Lawman with a 4-inch bull barrel. In the anime, Roy only draws this weapon once, during the third episode after Radinov attacks Rally and May.
Smith & Wesson Model 19
What seems to be a Smith & Wesson Model 19 is used by a cop holding up Bill Collins.
Smith and Wesson Schofield
A Smith and Wesson Schofield is seen in the Gunsmith Cats shop.
A Beretta M12 can be seen when Rally was being stopped and checked by gun runners in the first episode.
When Radinov attacks the ATF safehouse in the second episode, she guns down an agent attempting to fire a Micro Uzi. She then picks up the gun and kills another ATF agent with it.
In the same episode, when Rally and May are investigating the shipping yard, some of the thugs that attack are carrying Micro-Uzis.
Heckler & Koch MP5A5
During the warehouse firefight in the first episode, some of the thugs are carrying Heckler & Koch MP5A5s.
During the high speed chase in the second episode, Radinov draws a Steyr TMP and opens fire at Rally. Rally later shoots the gun out of her hand.
She also uses the M950 to hunt down Rally and May during the final showdown.
SA Vz. 61 Skorpion
A SA Vz. 61 Skorpion is seen on the wall of the Gunsmith Cats' home basement.
Sawn-Off Double Barreled Shotgun
In the opening of the OVA, Rally and May move in on a gun runner who jumped his bail. When he discovers the two bounty hunters are after him, he grabs a sawn-off double barreled shotgun. However, May gets the drop on him and stuns him with a gas grenade.
Mossberg 500 Bullpup
One of the burglars in the first episode arms himself with a Mossberg 500 Bullpup. He never gets a chance to fire the weapon, as he and his pals are caught off guard by Rally and quickly subdued.
A Mossberg 500 Mariner, with what appears to be wood furniture, is used by one of the gun runners during the warehouse fire fight in the first episode.
Regular Mossberg 500s are seen in the second episode, in the hands of an ATF agent when Radinov attacks the safehouse and used by one of the thugs in the shipping yard fight.
Pistol-Gripped Remington 870
Radinov uses this shotgun during the high speed chase in the second episode. It's a cut down Remington 870 with front and back pistol grips.
During the warehouse fight the first episode, Rally grabs a Franchi PA8 with a folding stock and blindfires it, hitting two thugs in the legs. It's colored incorrectly, it should be all black, but the horizontal lines on the grip, and the vent holes in the stock give it away as a Franchi shotgun.
In the first episode, in the aftermath of the robbery, an AK-47 can be seen lying on the floor of Rally's Gun Store.
In the second episode, Rally and May investigate the shipping yard and find a crate full of weapons. Among them, is a AKS-74U.
Steyr AUG HBAR
One of the burglars in the first episode arms himself with a Steyr AUG HBAR from Rally's weapon collection.
Steyr AUG Para
Later two gun runners in the warehouse fire fight are armed with Steyr AUG Paras.
An M16A2 was seen in the background at Rally's shop.
Light Machine Gun
One of the burglars helps himself to a M249 SAW from Rally's gun collection.
M15 Anti-Tank Mine
While going through the girls' stash, one of the burglars finds a box of M15 anti-tank mines. Interestingly, the mines are light blue like training munitions instead of OD green like a live mine.
Bonnie's Leg and Grey's Arm
These are references to the original Gunsmith Cats manga. A character named Bonnie had a prosthetic leg which housed a PM9, a French submachine gun which was notable for its ability to fold its magazine to lie along the barrel, making it very compact; her shoe also housed a bounding antipersonnel mine. Grey, another character, lost his hand thanks to Rally and replaced it with the blade weapon seen here, which is high-grade carbon steel and mounted on a launching mechanism powered by a car suspension spring.
Gunsmith Cats' wall of guns
Take your pick.