A lot of Meteora. Hit the Floor, Nobody's Listening, Easier to Run...
and their instrumental tracks like Cure for the Itch and Sessions. They are one of the best of the albums to me.
I haven't read anything because I don't want to know how they sound like, I wanna discover it myself. But have I seen the word "Slipknot"?.
The lenght of the songs is awesome, btw.
They might also change the structure of the order of the songs. Like, for example, playing Points of Authority or Lying from You near the end of the first set.
The first thing that came to my mind when I saw that picture with the acoustic guitar is that it'd be awesome if they did something like this, adding rap to it:
http://www.youtube.com/watch?v=IKSy7Y5u2lM