My favourites are ZJemptv, QualiaSoup, patcondell and TheThinkingAtheist. I just love their arguments and do sometimes use them in debates. They're all very good resources from which to obtain ammunition for debates.
What's your favourites?
Good atheist YouTube channels? (http://happyatheistforum.com/viewtopic.php?f=4&t=6189&p=101761&hilit=youtube+atheists#p101761) is a thread you might find useful.
I don't really have favourites Atheist YouTubers, however this is one of my favourite arguments for skepticism:
[youtube:2tesrk4a]http://www.youtube.com/watch?v=GZBlMwFnPns[/youtube:2tesrk4a]