The weapons in Fallout 3 - at least the majority of them - were made by Liquid Development. Now, as we know Fallout: New Vegas introduces a large amount of new weapons, that weren't in FO3. To me, these seem to have a somewhat different style than the FO3 "legacy" ones - were they done in-house by Obsidian, or by some other third-party? Or were they in fact done by Liquid Development too?

Obsdian

look for a video on youtube called: Fallout new vegas: weapons and technology.

Didn't find any youtube with that title, but yeah, that's kinda what I figured, explains the slightly different style of many of the NV weapons.

here, is this video

https://www.youtube.com/watch?v=cF94bmbt5rE