Home of Rhett & Link fans - the Mythical Beasts!
I know it's not GMM, but have you ever heard Rhett and Link's Ear Biscuits episodes with Phil and Julian? The podcast conversations tend to delve pretty deep.
I was going to suggest Matthias, but seeing he's on the list, how about the whole of Team Edge? :0 I'd love to see that whole group on GMM!
I like the inclusion of Wong Fu Productions! I might also suggest Ryan Higa, or maybe a musical artist such as David Choi or Kina Grannis.
I'd love to see Paint (Jon Cozart). And while we're on the music side, maybe Kurt Hugo Schneider?