Artillery

Artillery presents itself as world objects in Fallout 2 and Fallout: New Vegas, and appears as a unnamed artillery piece in Fallout 3.

Characteristics
Artillery pieces are pre-War weapons used by the United States Armed Forces. Some are mobile, some are stationary but all use the same basic principles and gunpowder as a propellant. They provide covering fire for ground forces, anti-air support, can soften up fortified targets or fill a role in testing new varieties of shells (most notably Saturnite).

A large number of these weapons were stored or fielded in various parts of the country, useless to anyone without the foresight to see an extremely valuable piece of weaponry.

Fallout 2

 * A howitzer can be used to gain access to the Sierra Army Depot, providing a wealth of resources.
 * The savant weapon smith Algernon in New Reno has been provided with a howitzer by Eldridge, the owner of the New Reno Arms, for maintenance. The weapon is to be added to his collection and stockpile of arms.

Fallout 3

 * The Talon Company possesses an unknown number of artillery pieces. They are never strictly identified as howitzers, yet given the level of pre-War technology at their disposal and the rarity of other forms of artillery, it is reasonable to assume the weapons are howitzers. Artillery strikes from the weapons can be called in on Seward Square and the super mutant behemoth at Takoma Park. Both include some form of operating instructions, which is a note near the signal switches.
 * The Enclave possess artillery in some form as well, as evidenced by the Sector artillery notes located at Adams Air Force Base. However, these weapons are only mentioned, as they do not have a means of being fired. The Enclave will instead fire from atop the Mobile Base Crawler using their Big Guns.

Fallout: New Vegas

 * The Boomers acquired several of these guns from Area 2. They are used to protect Nellis Air Force Base from strangers near and far, as well as preventing anyone from effectively spying on the base. Caesar mentions that some of his scouts were shelled at extreme distances. The Boomer guns were also used in unspoken negotiations with the New California Republic, who had attempted to shut off the base's water supply. In response, the Boomers shelled the water lines to the NCR Sharecropper Farms, prompting the NCR to turn the water back on at the base.
 * Dale Barton salvaged a howitzer from a military base in Yuma, Arizona and then sold it to Caesar's Legion. The Legion hopes to use it during the Second Battle of Hoover Dam for suppressing the 1st Reconnaissance Battalion and Veteran Ranger snipers, but without a Howitzer firing mechanism, they are unable to coax it to working order.

Anti-aircraft gun
An automated anti-aircraft gun is positioned at the top of Hoover Dam. It was built to protect the dam from attacks by Chinese aircraft, which never arrived due to the Great War. The New California Republic keep the gun in working order to prevent a surprise attack by aircraft. Despite this fact, it is not used during Veni, Vidi, Vici as it gets blown up by Caesar's Legion early in the battle. The gun can also be tampered with during the Legion quest Arizona Killer to assassinate the NCR president, Aaron Kimball, where the courier can rig the gun to explode, or reprogram it to shoot down Bear Force One.

Fixed artillery
Several fixed guns were positioned in Alaska to help safeguard the Alaskan Pipeline, however when the People's Liberation Army invaded the guns were seized and turned on the United States Armed Forces. During Operation: Anchorage the guns were finally silenced. How exactly control or destruction of the guns was carried out is unknown, as the only surviving record was a simulation which may or may not be entirely accurate in its portrayal of events.

The guns also make an appearance in Big MT, at the X-7a "Left Field" artillery launch. The guns at Big MT fire test rounds comprised of Saturnite (a space age material), one of these shells can be used in a test firing targeted at the X-7b "Boom Town" target zone. The resulting crater reveals a hidden cache that the player can loot.