whew, for a second there, I thought Pete Townshend was talking, until I heard the riff to Whole Lotta Love. That would have been a head-scratcher. The Who is great, he wrote great songs, but he shouldn't be in this list.
Jimmy Page, OTOH...
Many of us have seen It Might Get Loud... I didn't like it all that much, truthfully, but I really enjoyed when Page did this riff in front of The Edge and Jack White. Those two looked like they were going to cry with joy. (I think I nearly misted up, too.)