#1
what's the name of the thing that john mayer does in "stop this train?"

ben howard does it too through most of this:

http://www.youtube.com/watch?v=2ITHG--QRBg


basically, its a thumb slap at the same time as a string pluck/strum... gives the song percussion without interrupting the melody


anyone know what the technique is called?
sigless
#2
to be honest, I think you already have the answer. I have studied this technique for a few years now, and there is no standard name for it. I call and the pluck and chuck technique and I write a guitar series on it under that name. That's the best anyone has done that I know of. If you come up with something better, let me know. I cover all the heavy John Mayer stuff in my series, so you might want to check it out

***AlanHB link removed***