Favorite song to demo or test drive speakers?

Dire Straits -- You and Your Friend (the opening originally sold me on my KEF 104/2)

Eric Claption - Old Love (24 Nights)Pieces of a Dream - I Feel Like Signin'St Paul & the Broken Bones - I'm Torn UpRobert Plant & the Strange Sensation - Shine It All AroundBobby Lyle - Exotic LoveAlvin Lee & Ten Years After - Help MeAlex Skolnick Trio- UnboundAcoustic Alchemy - Against the Grain

Jan Hammer - "Darkness/Earth in Search of a Sun", and the whole album “First Seven Days”

Steely Dan:  “West of Hollywood”

Bach:  any good recording of “Toccata and Feuge in D Minor”

+1 Jan Hammer/Jeff beck song. Great choice. 
Walk on the Wild Side, Lou Reed. (Background singers!)

Poinciana by Keith Jarrett Trio, Live in Paris (drums first, then the most beautiful sounding piano—great for comparing DACs)

Follow Me Home, Dire Straits (soundstage test for ocean waves, then bongos, drums, then bass and various guitars...and then vocals). This track will mesmerize you on a good system.