I don't like Youtube much but my girlfriend religiously follows the Shaytards, Jenna Marbles, Glowzel (spelling?), and FluffeeTalks. I cannot tell you the number of times I've been in the midst of an epic ground battle in Call of Duty Black Ops, finally doing well after a night of torment by awesome shooter people, when the internet crashes because she decided to hop on and check out the latest videos she subscribes to.
that's bad... but The worst is when we're on level 24+ in Nazi Zombies or something. A Crash there means the night's just over man...
Anyway, because of her I have ended up watching some of all the above. I think I enjoy FluffeeTalks the most, though his intro drives me CRAZY when I'm not watching personally.