Led Zeppelin for two reasons. One, to piss off the "hardcore" fans who say Led is not Heavy Metal when in fact Rock historians credit Led (alongside Pink Floyd, Deep Purple and Black Sabbath) as pioneers and the biggest progenitor of the genre.
Two, because I just think they're the best in that list. Ok, that's not true. I prefer AC/DC over them but I wouldn't go so far as saying them Aussies are metal..