I subscribe to the official channels of favorites bands. Clutch has been doing YouTube performances for the past few weeks while they are not touring, and that's pretty cool.
But as far as YouTube specific content, I like channels that cover vintage audio and video tech. "Techmoan" is probably the largest of these, with almost a million subscribers. "Technology Connections" is also pretty huge, and does a good job detailing the history of tech that he covers. "VWestlife" tests out vintage A/V gear all the time, and is the most accessible 100K+ channel I know, responding to comments, and even leaving an occasional comment on smaller channels such as mine, which I appreciate.
8-bit Guy, LGR, and Nostalgia Nerd are all more computer oriented than vintage A/V gear, but I like vintage computers and software as well.