Being a White Stripes fan, I had heard about "It Might Get Loud" at least a year before it came out and anxiously awaited it's release. The film is described as "a documentary on the electric guitar from the point of view of three rock legends". The legends in this case are Jimmy Page (Led Zeppelin), Jack White (White Stipes, Raconteurs) and The Edge (U2).
I was fortunate enough to see it at the most excellent Red River Theatres in Concord, NH during it's theater run over the summer. If you didn't get to see it in the theaters, I highly recommend that you check it out at home. According to the official Sony Pictures website, it will be available on DVD and Blu-Ray on December 22nd.
I'm a huge fan of Jimmy Page and Jack White, so I would've also picked them if I had to pick only three (living) guitarists. I also like The Edge, whose inclusion adds some detail on effects, but my dream pick for the third guitarist would be Neil Young.