I love scishow!! Specially when they do the quiz episodes. I’ve watched many of the crashcourse ones too.
Minute physics, minute earth, now this world, seeker, etc are great channels too.
My guilty pleasures at the moment are the Nostalgia Critic (channel awesome) and Tom Ska (DarkSquidge).
But most of my subscriptions are CG channels with 3D animated shorts, and CG/3D tutorial channels (plus the official sites of the software I use), because that is what I do.
Did I mention I haven’t had cable in over 10 years now? 
(I do have netflix though, because that is mandatory)