Quite hard choice, to be frank.
My personal favourite is probably D'yer Maker. I don't know why but I think it's really nice, even though it's quite different from the rest of their stuff.
Runners up in no particular order would be: Heartbreaker, Immigrant Song (OOOOOAAAAAAAAAHHHHHHHHAAAAHHHH!!! indeed, sir kharbevnor), Babe, I'm Gonna Leave You, Black Dog, Rain Song (is it really called that? I've only got a shady mp3), Rock & Roll, Communication Breakdown, Whole Lotta Love, all their long live extravaganzas, everything else.