(from a TV Guide article: Matthew Fox's fearless, balls-to-the-wall performance)

http://www.idiomsite.com/ballstothe.htm

Dating back to the 1950's, this refers to nn all-out effort. The phrase originated from an aviation term. On airplanes, the throttle control handles and the fuel mixture are often topped with grips that are ball shaped, thus referring to pilots as "balls." If you push the ball forward close to the front wall of the cockpit your result would be a top speed.

http://www.urbandictionary.com/define.php?term=balls+to+the+wall

Term used by pilots. when accelerating quickly, the throttle is pushed all the way to the panel and the throttle lever (ball) actually touches the panel (wall). Hence, balls to the wall.

http://www.slate.com/id/2136001/

The phrase is essentially the aeronautical equivalent of the automotive "pedal to the metal."