On the Tax Prof Blog, Paul Caron reports on the recent work of his colleague, Adam Steinman, who documented the most heavily cited court cases in his discussion of Celotex (a Civ Pro I standby). Paul's blog entry includes a table of the Top 10. Seeing no tax cases, Paul generated his own Tax Top 10, which he also posts.
All this reminds me of the fascinating network analysis of court cases by Tom Smith of the University of San Diego Law School. (See, e.g, The Web of Law.) There is a lot of work to be done in this area. The digitization of the data + adequate computer power are relatively new phenomena.