Parks! The Parks is the fastest board that I know of. Its a board that you don't have to apply alot of pressure to get the board to cut. Because the fins have such an extreme angle the result is a board that is very sticky and quick when an edge is set whether cutting to the outside of a wake or building a progressive edge into the wake. The thing I noticed about this board was if you stood neutral or centered the board was very loose but when weight was set back or towards the rear it was very sticky. The board has the largest flat spot that Hyperlite has ever produced which took over as the largest abrupt popping board that Hyperlite has made since the Byerly. The Parks is said to be quick, fast, abrupt, and very unique in the way it performs on water. It is a board that like to be rode a particular way by a rider that desires certain board characteristics. They say this is the one board not ment to be ridin by a beginner rider. This board is advanced and unique in the way it rides. Anyway hope you find what your looking for. Take Care.
I found the O'brien Cobe to be way quicker than the Parks. We're talking scary fast here... It's not so much the speed that scares me, but the rate of acceleration.
Most LF boards with side fins are super quick too.
A third vote for the Balance. Very fast. I demo'd both and bought the Balance. Parks was good, but a bit too loose, I thought. The three fins on the Balance allow it to hook up and respond very quickly.