The following weapons were used in the OVA Appleseed:
Several Olympus Police officers in the OVA are armed with generic M1911 pistols.
One of the ill-fated terrorists at the beginning of the OVA carries a commercial Browning Hi-Power.
Several Olympus Police officers are seen carrying first generation Glock 17s.
Unidentified Suppressed Handgun
One of Sebastian's men uses an unidentified semi-automatic handgun to kill a security guard while his cohorts steal a squad of LandMates.
Colt MK IV Series 70
Deunan Knute's sidearm of choice is a Colt MK IV Series 70 .45 caliber pistol. Of all the weapons in the OVA, this one undoubtedly gets the most screentime.
Colt Combat Commander
Athena carries a Colt Combat Commander, which she lends to Deunan during the finale.
One of the plainclothes officers at the beginning of the OVA is armed with a MAC-11 submachine gun, which he has hidden under a magazine in the back seat of the officers' car.
Briareos Hecatonchires' weapon of choice is a MAC-10 submachine gun. Being a 7-foot tall, near-totally mechanical cyborg, he is easily able to fire the gun one-handed on full auto with minimal loss of control.
Heckler & Koch MP5A2
Several police officers are armed with H&K MP5A2s with slimline handguards.
Heckler & Koch MP5SD3
Several Olympus Police officers are armed with a H&K MP5SD3 outfitted with solid stocks.
One of the thugs that Deunan and Briareos try to interrogate opens fire on them with a MP40.
Two of the cyborg terrorists in the opening sequence are armed with M16A1 rifles. In a possible continuity error, in the next shot, the rifle has a 20 round magazine instead of the 30 round magazine it started out with.
Heckler & Koch PSG-1
The S.W.A.T. snipers during the first terrorist attack are seen using a H&K PSG-1 sniper rifles outfitted with bipods.
Briareos is seen using an extremely large, high caliber bullpup rifle when Hitomi is kidnapped. This is a fictional rifle that appears several times in the manga and is usually used by LandMates. Given Briareos' size and strength, he is able to use this weapon like a regular assault rifle.
The officers who try to arrest the terrorist at the beginning of the OVA wind up on the business end of a Browning M1919 mounted to an M2 tripod.
All of the patrol helicopters used by the Olympus Air Police are equipped with GAU-19/A Gatling guns.
In addition to its battery of cannons, the Multipede Cannon is equipped with a pair of M61 Vulcan rotary guns.
Heckler & Koch HK69A1
The ES.W.A.T. team that responds to the initial terrorist attack uses HK69 grenade launchers to fill the terrorists' holdout with CS gas.
During the confrontation with Calon, Deunan uses a M79 grenade launcher outfitted with a red dot scope. Given the fact that she's confronting a LandMate, this configuration doesn't seem as absurd as it would anywhere else.
The LandMates (a halfway point between a mecha and power armor) seen in the OVA use a set of specialized weapons for LandMate-on-LandMate combat. The rifles carried by the ES.W.A.T.'s CADMOS LandMates appear to be simple bullpup rifles reminiscent of the Norinco Type 86S, while the industrial LandMates used by the HLU terrorists carry rifles with a conventional LR-300-esque design. All of these weapons have been scaled up to accommodate the larger dimensions of a LandMate and appear to fire large caliber armor-piercing rounds anywhere between 12mm to 20mm.