I recently learned that Peter Sneath died last Friday. I suspect that if I were to poll graduate students in my department, few of them would recognize the name. But anyone who's old enough to remember the battles between cladists and pheneticists will certainly remember the book Numerical Taxonomy (first edition Sokal and Sneath, second edition [the one I own] Sneath and Sokal). It's fair to say that along with Robert Sokal and others, Sneath's use of computers to analyze variation and classify species revolutionized taxonomy. Although biologists no longer use the clustering algorithms they describe for classification, those algorithms are the foundation of modern clustering algorithms that are used in many different fields.
Joe Felsenstein has a nice appreciation of Sneath at Panda's Thumb.