When I started watching minecraft videos, it wasn't of anyone in particular. It was a random Redstone build here, a time lapse there. Then I stumbled upon CaptainSparklez and the whole Mianite series. I had never really looked at minecraft from a massive role playing perspective before that. Needless to say, I binge watched both seasons of it. Season 2 was what actually got me started playing modded. So sparkles is definitely towards the top of my list. Through him, I started watching X33n more recently. I like their back and forth banter / teasing.
Beyond that, Mumbo was the one that introduced me to the rest of the hermits. I subscribed to all of them when season 5 started and currently don't miss an episode of Ren, of course, Mumbo, Scar, Xisuma, or Iskall. I'll watch Cub, Wells, and False just to check in with their progress, but not regularly.
I also really enjoy watching Etho. I like the fact that he does a good balance of technical and aesthetic builds.