I'd say the manikins in Skyrim are right out of mods (since morrowind, manikins have been a big deal in mods, featured in basically every dwelling mod). But it wasnt so much as taking from a single mod, but seeing a trend in the popular mods.
Also, Serana from the dawnguard DLC seems like almost a copy of the big companion mods for Morrowind and Oblivion (which for some reason most of them are attractive young female companions and/or vampires).
The combat in skyrim, shield bashing and decapitation, those were big features of the Deadly Reflexes mod for oblivion, one of the most popular mods. Of course those are pretty general improvements to the combat though.
And the hearthfire DLC, that's basically a glorified settlement building mod (which were also very popular)
I dunno, there was a lot in skyrim when i first played it that seemed like they used ideas from popular mods for oblivion and morrowind. Maybe not quite as blatant as new vegas, but they were pretty noticeable to me.
Yeah, it's just an old skill brought back essentially.