I’ll can think of two different ones, in alphabetical order:
1) Big hybrid electrostatic from MartinLogan in the previous iteration of HiFi Buys in Atlanta's Buckhead neighborhood, playing the Gardiner/Philharmonia read of Holst's "The Planets" on CD. I was maybe 13, 14. I'd never heard an orchestra sound so "in the room" before, like you could reach out and grab the baton. They also looked so cool. I think that era's ML's are better styled than any subsequent generation. I do not remember, nor care about, the "associated equipment." I'm sure it was expensive, and it was from an era before room correction, so...whatever. Funny, every time after that I heard MLs I disliked them, until the most recent iteration with end-fire array woofers and ARC, set up at a trade show with Anthem electronics. Those sounded quite nice, and were the second or third best speakers at that show after Salon2's set up by Mr. Voecks or F36s also set up by Kevin.
2) Tannoy D700 set up by Gordon Waters in another long-gone metro Atlanta audio shop, Audio Atlanta around the Marietta Square, mid-late 1990s. Recording was Stevie Ray Vaughan's live "Little Wing" cover. The dynamics, imaging, and clarity had me listening to nothing but coaxes from 5"-12" from the mid-1990s until I heard the JBL LSR705i a couple years ago. Again, there was associated equipment. It was besides the point.