This is an awesome one, didn't finish yet but I will later. Tyson is the best and I generally enjoy hearing Dawkins talk, especially when it's about something other than atheism or the whole evolution/creationism thing, which at this point I find a little grating and redundant (though I fully admit to thinking he was the best thing ever when I was a bit younger and more militant in my "non-belief" or whatever you want to call it). The part where he's inquiring about the expansion of the universe was really good for me personally, since it's something I find really fuckin' hard to conceptualize and he was basically asking the same questions that were popping up in my head as Tyson spoke.
This is another one I like, with Dawkins and Lawrence Krauss, who is always a great speaker, on the topic of how "something could have come from nothing"
