So many classics, so many hits, although they do appeal to a more...*ahem*, "select" audience.
I had to vote for 'Heavy Duty', I think it's an underappreciated song. I like how the plodding verse gives way to the triumphant chorus, underscoring the inevitable majesty of rock. Oh wait a sec, there's another Tap classic, 'The Majesty of Rock'. Damn, too many choose.....brain aneurysm!