Best song for immediate impact when presenting or testing?

Kandace Springs Breakdown
La Vie (Pop Mix) Philippe Saisse
Elton John Rocket Man    Honky Chateau
Gordon Lightfoot   If You Could Read My Mind 
It Ain't No Use   Trombone Shorty   Parking Lot Symphony
Lake Street Dive  I Want You Back    Fun Machine
Whirlpool  Seal  The Rare Collection
a-ha  The Sun Always Shines on TV   MTV Unplugged Summer Solstice
Michael Hedges   Aerial Boundaries   Pure Michael Hedges
Splendor in the Grass   Pink Martini
God of Wonders  Paul Baloche   (live)
The Ladder  Paula Cole   Harbinger
I Don't Know   Shawn Colvin   The Greatest 60's Album 
Along the Road  Dan Fogelberg   Live at Carnegie Hall
Friends   Brandt Brauer Frick Ensemble    Mr Machine
Be Here Now   Ray LaMontagne   Til the Sun Turns Black
Driving    Everything But the Girl    Acoustic
(Sittin' On) The Dock of the Bay  Sara Barieilles   Brave Enough: Live at the Variety Playhouse
The Windmills of Your Mind   Alison Moyet   Voice (reissue Deluxe)
Cantaloop (Flip Out)  Manhattan Transfer   The Junction 
Humilitas    Lesiem    Auracle 

I didn't select these to impress people, but are some that I use in assessment of audio system performance. However, with an extreme system several of these are impressive performances.  In reviewing I use lists such as this to not only tell the limits of the system's performance, but tune the system. 

+1 Factory Girl

Vinyl: Neil Diamond, Hot (August Night) side 3 "Canta Libre" or "Morningside"

Vinyl: Pink Floyd (Dark Side of the Moon) "Time"

Vinyl: Herb Alpert't Tijuana  Brass (Whipped Cream & Other Delights) any cut

CD: Hillbilly Winos (Live from the Living Room) any cut

CD: Van Morrison (Avalon Sunset) "These Are The Days"

CD: Pink Floyd (Division Bell) "High Hopes" or any other cut

CD: Sting (all this time) "Perfect Love", "Moon Over Bourbon Street"

CD: Jane Monheit (The Very Best Of) "Hit The Road To Dreamland"

CD: Hugh Masekela (hope) "Stimela" (The Coal Train)

Anything Sade

So many more that I might choose......Jim

My two cents..

1.  Dave Brubeck’s “Take Five” for all the reasons previously cited.  This one’s a jazz classic.

2.  Jazz at the Pawnshop, vol 1, especially “Limehouse Blues” & “High Life”.  Not only terrific jazz but masterfully engineered. The detail, the dynamic range & the imaging will really shine on a good system. I especially like the interplay between the alto sax and the marimbas.  My face always hurts after a good listen (too much smiling)

3.  A recent find & current fav is Cyndi Lauper’s “At Last”, title track & “Until You Come Back to Me” in particular. Vocals can really show the strengths of a nice system, as well as expose weaknesses.  Cyndi’s voice will test your system and please your ears.  A two-fer.

Great thread, OP, got me listening to some old stone-cold classics and adding many new ones to my "must listen to" list.  Here's a couple more - 

Billy Cobham - "Searching for the Right Door/Spectrum" from Spectrum.  Great drums on intro and throughout, excellent PRAT qualities.  

Massive Attack - "Inertia Creeps" from Mezzanine.

Lake Street Dive - "Mistakes" from Side Pony.

First Aid Kit - "Emmylou" from The Lion's Roar.

Morphine - "Dawna/Bueno" from Cure for Pain.

And lately I keep returning to the recent Handel's Italian Cantatas performed by Sabine Devieilhe, Lea Desandre, and Emmanuelle Haim.