A few months ago, I played in a Simul vs. Michael Khodarkovsky at my school. Michael is a retired master, now a teacher, who played second board to Garry Kasparov in the world championship! He wrote a book on the grunfeld, but I forget what it is called.
This was actually a pretty nice game. I was actually up a pawn for quite some time until he forked my rooks. (Ouch)