In order of how they came to my mind as I was typing this, not necessarily preference...
Forgotten Weapons- The vast number of crazy, cool, and just weird firearms that have been produced- commercially- is truly staggering.
Alec Steele- This kid's drive and love for what he does is mind blowing. I wish 1/2 of the US work force had 1/2 the drive he does. Truly, the kind of foreign labor we need to be importing into this country. If i have to chose a "favorite," this is it.
This Old Tony- I can't really explain my YouTube preferences. I'm not a black smith (See above). I'm not a machinist. But, watching people make stuff is really cool- especially when the product- both the actual item and the video- are superb. See below.
Powerball Tools- Another I can't explain. You could can fit my motley assortment of tools in a small roll-around tool chest, and my need for tools is generally smaller than my acumen with them. But, this guy puts out top quality Youtube content.
C&Arsenal- This is one of those that I can turn on and just let play in the background. Lots of good history and cool old rifles. I'm not sure what gives May the street cred to opine on what makes for a good infantry weapon. The videos are generally superbly edited.
Anvil- Mark Novak, just another skilled professional plying his trade. Repairing, restoring, conserving, and bringing back from the dead cool old firearms. No "assembly" here. This appears to be actual gunsmithing, though I'm not a gunsmith.
InRange- I like the match stuff- especially when they put the weirder guns to the test on the clock. But, Karl is way, WAY, full of himself. From what I can tell, neither he nor Ian have been in the military (and neither have I). But, that doesn't stop either of them from anointing the best tool(s) for the job. Karl can keep his self-absorbed SJW bloviating to himself- and he seems to be getting worse and worse about this. Is Youtube "fame" going to his head?
Chewjitsu- Must have mentality/attitude/ego-check for long term success in a martial arts/MMA gym. And, some really great technique content as well.
Channels I generally don't watch?
IV8888- I can't really put my finger on the "why," but everything here is "cringy" on some level. YMMV
MrGnG- I guess this one is okay, but seems a little shillish on occasion. Also, there tends to be a low information content to video length ratio. Not NutnFancy low, but not great either. I have watched some reviews that I found informative. I don't subscribe to the channel, but may watch a vid if it shows up in the search results.
MAC- Not entertaining. Not particularly informative. Seems to follow the Chicken Little school of 2A advocacy.
Hickoc45- Old guy shooting guns. No information. Meh.
Pretty much any of the 2A advocacy "news" channels. See MAC above.