From publisher blurb:
This article is intended to flesh out variant futuristic weapons produced during the time of the Ancients, as well as giving brief information on the companies that made them. None of these weapons were common even during the technological heyday of the human race, kept from mainstream use either due to high costs or faulty production and unpredictable defects.
The idea here is to present alternative choices to the energy weapons presented in the game; cheaper, more easily constructed, or even more powerful variations. These weapons can be used any way you want, either as unusual items in a treasure pile, something unique for the scav character to find with his ruin picking pastime, or as "bargain deals" in any wasteland marketplace.