I, like others, have more than a favorite, but generally use TRI-X or delta 100 for film and Rodinal, D76 (or ID11) and microphen. If I should restrict myself to a single film and developer I would go for TRI-X and D76 for the great flexibility of both.

Yet I believe that your question should be interpreted as: "What do you believe is the best combo to start with?"
If this is the question, the answer is rather different: Tri-x or FP4 for ease of process and a good tonal range, depending if you mainly shoot in low or high light (I would had HP5 but I prefer the grain of TRI-X); rodinal for its ease of use, exceptional shelf keeping, tone rendition and it's ability to preserve the grain structure of the film.