A few that haven't been mentioned, also subbed to many of the mentioned ones too.
ArcLight Fab - Aaron Kaufman's company (Main mechanic from Fast'n'Loud / Gas Monkey Garage)
Taylor Ray - Budget drift guy in America, can get a bit annoying
MotionAutoTV - Colorado based automotive YouTuber, does some great builds and generally just produces a lot of interesting automotive /mechanical content
Adam White - He's rebuilding a mini...or building as it seemed to start off as mostly rust
AutoAddiction - For Nurburgring crash videos
Beavis Motorsport - Aussie building a time attack MX5
eGarage - Produces some well made content
Emelia Hartford - Girl drifting an LS converted 240 although can be a bit annoying / clickbaity at times
Flying Sparks Garage - Couple that rebuild vehicles properly
Grenade Motorsports - This guy basically just fits classic cars onto modern chassis on a budget
Jonathan Ward - This guy & his company build some fantastic classics with modern gear to a very high standard
Missleworks - Colorado based fabrication guy, incredible work with a welder
Moto Madness - For hilarious bike incidents
Mr VRod - American with a Harley VRod in LA, fun guy
My Classic Car TV - Guy visits classic shows in America and features cars
Pneuma Chris - UK based guy who loves Subarus, has a Brat and an SVX he's building
Sarah-n-Tuned - American girl, often amusing innuendos and interesting cars
Speed Academy - Canadian guys that build / work on cars
The House of Muscle - Mike Musto from Drive has his show on it's own YT channel now, basically just big HP American cars.