BPS.Space: Dude building model rockets & flight controllers. Just landed a model rocket propulsively, video out soon - https://www.youtube.com/c/BPSspace
Overall: Applied Science Chemistry: Explosions and Fire Nile Red Electronics: Dave at EEVBLOG Phil’s Lab
As well as the main Explosions and Fire channel there is also Extractions and Ire - run by the same person but less focused on energetics and often goes into more depth on the chemistry.
If anyone is a history nerd, there are some folks who put together really professional videos on the two World Wars, and the events surrounding it. The WW2 channel is particularly good, as they do week-by-week for the whole 6 years. They're in 1943 right now. An impressive work.
I happen to have a list of channels I found fun and/or interesting at hand (https://defanor.uberspace.net/links.xhtml#Videos>), so here's a rather long one: Cody's Lab, How To Make Everything, Isaac Arthur, Linus Tech Tips, Numberphile, Stand-up Maths, Computerphile, Veritasium, SmarterEveryDay, Adam Savage's Tested, The 8-Bit Guy, Primitive Technology, StanfordUniversity, Geek & Sundry, Viva La Dirt League, Sixty Symbols, The Royal Institution, Harry Rogers, Ben & Lois Orford, 3Blue1Brown, David Butler, PBS Eons (and PBS channels are nice in general), Adam Ruins Everything, OverSimplified, Sean Carroll's The Biggest Ideas in the Universe, Economics Explained, minutephysics, ElectroBOOM, NileRed, Stuff Made Here, GreatScott!, Electrician U, The Honest Carpenter, Fermilab, my mechanics, Hand Tool Rescue, Technology Connections, Practical Engineering (practical.engineering), Machine Thinking, Jeremy Fielding, Wristwatch Revival, StarTalk with Neil deGrasse Tyson, Matthew Fairbanks, Weird History, Nutty History, Modern History TV, Thoughty2, Ordinary Things, Grandpa Amu, AvE, Townsends, Tom Scott, Applied Science, Wondastic Tech.
Everything's really great so far in here, but there's Applied Science. He makes, and very clearly explains, what I can best describe as advanced materials in his shed.