For me it's DJ Peach Cobbler. I've been watching his videos since he had around 2,000 subscribers. Now it's nearly 450,000.
He used to mostly make videos on games, now he does a lot of history stuff too. He also has a little satirical news show, and a few tasteful shitposts. A really diverse YouTube channel.
What's your favorite YouTube channel that's not a mainstream big-name like pewdiepie, mrbeast, ksi, etc...?
Matt Brown - security researcher and bug bounty hunter
Robert Murray Smith - general mechanical engineering tinkering, lots to learn
TheCod3r - console and other electronic repairs
Wesley Kagan - builds cars but is just an overall genius and entertaining
Joe Grand - hacker, genius
There are more popular/sometimes better people and channels in each genre but I've stuck to those with under 1 million sub's. I'll assume people like Colin Furze, Ben Eater, Computerphile are already too well known for this thread
Very interesting list! I am especially curious about Matt Brown's videos. Thanks!