Simply who made them? I know Poseidon made some energy weapons I think, that's all that comes to mind right now.

http://fallout.gamepedia.com/Mauser

http://fallout.gamepedia.com/Colt

http://fallout.gamepedia.com/SIG-Sauer

Magnum Research Inc. (Desert Eagle)

http://fallout.gamepedia.com/Heckler_%26_Koch

http://fallout.gamepedia.com/Winchester

http://fallout.gamepedia.com/Rockwell

http://fallout.gamepedia.com/Pancor

http://fallout.gamepedia.com/Smith_%26_Wesson

Then we have other companies such as: http://fallout.gamepedia.com/Gaston_Glock & http://fallout.gamepedia.com/Wattz which made energy weapons. H&K also made the Gatling Laser. Winchester also made plasma rifles.