For a while my favorite song was Don't Stop Believin' - Journey, however i think at this moment i dont really have one. Been listening to alot of Breaks (Dj Baby Anne, Dj Icey, Future Sounds of Breaks, Exzact) lately, switching out from my usual routine of Drum and Bass (Methodus, Dj Roots, Shy FX, DB).
However, i will say Dawn Over a New World - Dragonforce, might be up there..
As far as my favourite song of all time, that would of course be Babe I'm Gonna Leave You - Led Zeppelin.