I've subscribed to a whole bunch more, so I figure I'll highlight the ones I think are most unusual, the ones that aren't quite like any other YouTube channel I know of.
Clint's Reptiles: Described by like half the comments as "the Bob Ross of reptiles," but I admit I've never been a fan of Bob Ross. On the other hand, watching a psychotically cheerful Mormon with a PhD in evolutionary biology describe why every reptile is "possibly the greatest pet reptile you could ever have" is possibly one of the greatest YouTube experiences you could ever have.
Worldbuilding Notes: Worldbuilding is a passion of mine, however I'm less fond of the worldbuilding community, and especially worldbuilding YouTube channels, which usually tell me what I already know. But this channel, initially created by a Polish woman to practice her Lojban, is just fascinating. (The first five videos are Lojban with English subs, the rest are in English.) The worlds she creates are really interesting, and her voice and the cute cartoons she makes (somewhat similar to
Extra Credits, but usually prettier), just make these videos a joy to watch.
Counter Arguments: I debated including this one, because it's an explicitly political channel, but I realized it's the only political channel I'm subscribed to. It's a channel devoted to demolishing bad arguments, mixed with random rants on things like "nice" drivers and YouTube's fair use policy. He also has weird and vaguely-related mashups at the end, which are what usually what result in him getting copyright claims and losing monetization (which also makes it questionably fair use, since they're not essential to his argument, a point he actually misses on his video on that subject), and reuploads them with alternate endings when that happens, as well as reuploading when he feels he made a major mistake in a major video, which is something I approve of.
Atomic Shrimp: An English guy whose scambaiting videos started appearing in my feed, but I wouldn't have subbed over scambaiting, and I rarely watch such videos. No, what got to me is that in his scambaiting videos, he says something to the effect of "I do a lot of stuff, so if you're going to sub for the scambaiting and then complain that you're getting irrelevant stuff in your feed, don't sub." So I looked at his other stuff. It's eclectic, but a lot of it is pretty interesting.
I did a thing: Oh my god, if I haven't discovered Australia's YouTube channel, that means there's another person exactly like him in the same country, and isn't that a disturbing thought? But seriously, this guy does interesting things, while trying to present himself as extremely incompetent and slightly insane, and the result is weirdly fascinating. Honestly, I think that this might be possibly the best channel on YouTube.
I've subbed a lot of other very interesting, mostly very competent channels, but these five, like I said, are weird and quirky enough I feel I have to share them. Especially Worldbuilding Notes and I did a thing. I
really like those two, have binge-watched their entire and near-entire archives respectively, and they're among the handful of YouTube channels I have notifications enabled for.