Forgotten Weapons. Guy named Ian goes into meticulous detail about mostly obscure guns he finds at various places. Mostly auction houses but he's also been invited into the non-public armories of nations and armorers. He's a total gun and history geek.
Gus Johnson makes some really funny videos sometimes.
Dunkey makes some really funny video game videos, and when he's reviewing something semi-seriously he's very honest.
SavageGeese is a good car reviewer, pretty thorough and covers some bases that almost nobody else does. Very honest about his opinion which is not common in the car journalism field.
Harry's Garage is a car channel run by a guy who founded Evo magazine. He's like a kid that grew old but never grew up. Awesome enthusiasm for fun cars. He also introduced the mechanic working on his classic Lamborghini Espada to producing YouTube videos, Tyrell's Classic Workshop.
Historia Civilis is an acquired taste but he puts together episodes in history in an entertaining way, illustrated in a simple and often silly style.