Along with a star-studded bunch of surprise guests, Jay-Z brought John out to play guitar on his 9/11 Answer the Call charity concert at Madison Square Garden in 2009. John and Jay started with “U Don't Know." Then after briefly shredding through some of Jay's hits like “Dirt Off Your Shoulder” and “Run This Town,” the two launched into “D.OA.” It was pretty bad ass, to say the least.