I believe that while one could give an answer to your question the answer would depend on multiple factors. What time of year, time of day, before or after a meal, company on hand, etc.
I have had a lot of good cigars but to pick one exclusively over all others would be impossible and unrealistic.
My pick at this moment in time (Sunday evening, 7/20/2003) would be a CAO Impanema. Tomorrow night it could be a PAN or Hemingway Classic or several other cigars.
Just my .02 worth.
John