many favorites (I know its impossible :D but I cannot choose)
I usually listen a period the complete symphonies of one composer and after a while another, so all symphonies kind of mix up in my head...
Shostakovich 10 (and 1 and 4 are funny, 5 and 6 are great. The war-triology (7-9) is superb, 11 and 12 are slow but massive. 13 is the first I heard of him, opening is huge!)
Prokofiev 5 (1 is funny, 2 and 3 are crazy :D ; 4 is relaxed 5 till 7 are great too...)
Brahms 1 and 3 (2 is okay... 4 too, it used to be a fav, still a beauty, but heard it too often)
Tschaikofksy's Manfred symphony , and 5th and 6th, in fact all are good, 2 and 3 oh... (anyone said him already?)
Mahler only the 6th (maybe 1 and 2 also...)
I like to mention the symphonietta by Poulenc, and the 2nd by Khrennikov as honorary mentions