What is the best ergonomic mouse on the market for the elimination of wrist pain and strain?

Let's assume cost isn't the greatest factor...(strain prevention overriding).

I spend a good amount of time in front of the computer, and have found that split ergonomic keyboards are really effective in preventing stress in the wrists.

Unfortunately, I've been much less successful in finding the perfect mouse.

I had been using a Logitech Ergonomic Trackball Mouse, and that hadn't helped; my wrist and the nerves in some of my fingers are still very sore. I recently purchased one of their non-track ball ergonomic wireless mice--which is definitely better (and really cool), but also not 100% effective.

Is there a mouse out there that completely alleviates the wrist strain, and best prevents the onset of, or accomodates those who suffer from carpal tunnel?