The Tesla cannon is a pre-War designed shoulder-mounted heavy directed energy weapon, designed to replace conventional anti-tank weapons. Based on Nikola Tesla's designs, the weapon entered limited production before the war and remains a rare sight in the wasteland. However, it remains a powerful tool in the hands of a skilled user, as the focused energy blast will not only deliver massive damage to the target, but the nature of the blast will also deliver a potent electric shock.
The modified Tesla cannon employed by Lyons' Brotherhood of Steel is far more powerful than the pre-war Tesla cannon. Discharging a large electrical impulse upon impact with a much larger area of effect. This explosive damage makes the Lyon's model far more suitable for anti-Vertibird use.
The Tesla-Beaton prototype appears to be similar to the Tesla cannon, but with an orange glow instead of blue, and a fully encased energy emitter. It also has several exposed wires and various lights attached to the casing, giving it a more makeshift appearance. Prior to patch 188.8.131.522, each shot expended 45 electron charge packs, but it now expends six electron charge packs per shot, with a magazine capacity of 24. Also, the patch removed the prototype's AOE blast damage. Unlike the original Tesla cannon, it only has half the HP. This is likely due to it being in the prototype stage. Because of this issue, the need for constant repair makes it a less practical weapon for repeated use.
Due to it previously firing only one shot per reload, it ejects electron charge packs every shot, which is strange, considering only one is loaded. Also, the electron charge pack will not appear after one shot is fired, and the end of the cannon is retracted, but it still ejects another per shot.
The Tesla cannon was originally to be featured in the canceled Fallout: Brotherhood of Steel 2, bearing no resemblance to the weapon in Broken Steel. Described as a "high-powered mass-cannon throwing tessellated plasma forward in an orgy of death and destruction" in the Fallout: Brotherhood of Steel 2 design document, it was to be the so-called "uber-weapon" of player character Maxus. "Uber-weapons" were to be unique weapons for each player character which had to be assembled from 5 parts over the course of the game, or the player could have a NPC assemble one for them. One of the five parts for this weapon was a Tesla coil.
Nikola Tesla really did try to create a directed energy weapon but it would have been a particle beam weapon called a "Teleforce," something that would be immensely complicated to create.
The following is based on unverified behind the scenes information and has not been confirmed by canon sources.
PCPlaystation 3Xbox 360 Sometimes the robots surrounding the crashed vertibird will not appear. If reloading a save near the crash site after picking up the weapon the robots will spawn all around you. [verified]
Playstation 3 In some cases, the clear encasing on the cannon will not show the Tesla coil animation and instead always stay glowing orange, reloading a saved game or fast traveling will fix this. [verified]
Playstation 3Xbox 360 After patch 1.5/184.108.40.2064, when looking from the third person, the Tesla-Beaton prototype will eject the electron charge pack in the back of the cannon after the first shot, and then seemingly eject electron charge packs out of nowhere during any shots after the first one. This can be remedied by reloading after each shot, though it is not recommended. [verified]
↑The Lone Wanderer: "Olney Powerworks? What's there?" Tristan: "Hopefully you'll be able to find a Tesla coil, an experimental device from before the war. Our scribes need it to complete a little surprise they've been preparing for the Enclave. Get there, get the coil, and get back as safely and quickly as possible. Any questions?" (DLC03Tristan.txt)