The AER9 was actually not the top laser rifle in service at the time of the Great War. The model line went up to the state-of-the-art AER12, which saw service in a handful of specialty units. The reason that the AER9 is much more commonly found is that it was much sturdier and more reliable than the models that followed.
The AER9 features a titanium housed crystal array which proved to withstand long years of exposure to the elements much better than the gold alloy housing of the later models. As a result, the crystal arrays stayed focused within operating parameters, rather than falling completely out of focus like the newer models. Power is drawn from microfusion cells and processed through a wave/particle diverter manufactured by General Atomics International. The diverters are protected by a carbon-fiber housing, preventing frequent malfunction, but when a diverter fails the weapon becomes unusable.
As with all energy weapons, the AER9 can suffer from poor performance if not properly maintained. The crystal arrays and non-mechanical components are delicate and if not properly serviced can lead to a loss of beam intensity, overheating, and energy regulation failure.
While identical in appearance to the laser rifle, it does 5 more damage and also comes equipped with a larger magazine, with 30 shots instead of the standard 24. It is also 80% more durable than the standard laser rifle with 800 more hit points.
Metal BlasterThe Pitt (add-on) - This unique variant of the AER9 fires nine beams at once, using one microfusion cell similar to the Protectron's Gaze laser pistol. This feature, coupled with its remarkably high damage-per-shot makes it a devastating short to close-range weapon, though its effectiveness greatly diminishes at a range with the "shotgun effect". It can be obtained by bringing fifty steel ingots to Everett in The Pitt.
Tri-beam laser rifleBroken Steel- The tri-beam laser rifle is a variant of the AER9 that fires three high-powered beams per shot - similar to the Metal Blaster - though it does require three microfusion cells every time the trigger is pulled. This weapon is not unique, dropped from super mutant overlords and is not repairable with anything but other tri-beam laser rifles. It was first made available in Broken Steel.
The following is based on Fallout 3 cut content and has not been confirmed by canon sources.
Operation: Anchorageadd-on includes an unused DLC-specific version of the laser rifle. It is identical to the normal laser rifle in both statistics and appearance. Its intended purpose in the DLC is unknown and it was cut from the final release, rendering it accessible only through the use of console commands.
A "demo" version of the laser rifle is included in Fallout 3, presumably left from the game's E3 demo. It does one point less damage per shot and less than half the critical damage than the standard variant, but has a much higher critical chance percentage. It is not used anywhere in the game and is only accessible through the use of console commands.
End of information based on Fallout 3 cut content.
Biwwy offers to sell his unique laser rifle to you in Little Lamplight for 500 caps because he has been kicked off the scavenger team and no longer goes out on patrols - he no longer needs a gun, but figures that you might.
With sufficient Barter skill, you can haggle the price down to 250 caps. If you have the Child at Heartperk, you can obtain the Wazer Wifle for free with no option to pay anything for it. Also note that if you have a high enough Barter skill you must buy it for 250 caps, that is if you can't pay the higher price.
ps3xbox360 It is possible to obtain two copies of the Wazer Wifle. The steps necessary to obtain two of the weapons must be done prior to initiating any dialogue with Biwwy, or no dialogue related to the weapon will display after obtaining it by theft. First, pickpocket Biwwy's microfusion cells, then leave and re-enter the Great Chamber(i.e. force a system load). After re-entering the Great Chamber Biwwy will have the Wazer Wifle in his inventory. Pickpocket it and proceed to enter dialogue to him. He will still be offering one or more options to obtain it, allowing the player to acquire another one. The one acquired via dialogue will be in a higher state of repair condition than the one that is stolen. Note, having the child at heart perk or a high barter skill affects Biwwy's dialogue options.
There were numerous rumors that this weapon can be used by Dogmeat. However, Dogmeat is a creature that cannot equip weapons. Using showinventory a weapon gets tagged with [CANNOT EQUIP]. You can force him to wear weapons using the console commandequipitem, and the weapons will drag along on the ground, but because he is not human and is a creature he won't be able to use it - there are no glitches that allow this to happen either. The thread that started it at somethingawful.com, with a picture (named shhhthisisajoke).