Like many who've posted above I have no one favourite symphony but I have great fondness, among several already cited, for Panufnik's 3rd. And Pettersson's 7th. And Nielsen's 4th, Sibelius's 7th, Hovhaness's 2nd (of 63).... and, good grief, Mozart! Numbers 34-41 inclusive (yes I know there's no 37) for a start - not to mention plenty of Haydn's. Bruckner's 3rd to 9th, Mahler's, er, all of them, Shostakovich 15 (and most of the other 14).