Gopher is an excellent choice for Fallout 3, New Vegas and Skyrim mods.
He also does let's plays, he's still active, and makes regular content, along with twitch streaming.
Alchestbreach is another good youtuber, he does GUN mod showcases and Nexus mods.
He's hilarious, and very light hearted.
MCDReviews is another good one, but he only reviews Nexus mods unfortunately. :/
Darkfiregaming used to make a lot of amazing content, but he's gone off the radar, according to his channel he was active three months ago..
He had some of the best reviews for Fallout 3 Mods..