'Black Dog' (1971)
Arguably the most badass Led Zeppelin riff: It was cooked up by Jones, who had a Muddy Waters song stuck in his head. Page turned it into a chain-saw ballet on his Les Paul over Bonzo's stealth groove, with snarling multitracked rhythm guitar tearing up the midsection. But Plant's vocal come-on – "Hey, hey, mama, said the way you move/Gonna make you sweat, gonna make you groove" – brings the real alchemy. It may not be Shakespeare, but as Plant later said, songs like "Black Dog" "make their point."