The Rolling Stones: The Brussels Affair (1973)
For me, much of the appeal lies in lead guitarist Mick Taylor. However great his contributions to the band's studio work, they're dwarfed by his live playing, his relentless slide guitar dominating a number of tracks (while simultaneously driving Keith Richards to step it up a notch as well, with some tremendous interplay between the two).
Highlights are... well, everything's a highlight. But "Gimme Shelter" is raging. Keith's frontman moment, "Happy," is a blast. "You Can't Always Get What You Want" goes on for days, and you still wish Taylor would play just a bit longer. I suppose the only negative is that some of the songs from the prior year are dropped to make room for a few from the recently-released Goats Head Soup. And while they're not bad, Goats was a bit of a drop-off after the unrivaled run of Let It Bleed, Sticky Fingers, and Exile on Main Street. (Still, while it's no "Bitch," a highlight of the prior tour, "Heartbreaker" is another chance for Mick T & Keef to go a little nuts.)
For awhile this was made available as an official archives release, in superb quality, though I'm not sure if that's still the case; for some reason, it seems to have been dropped, while lesser archive releases from later in their career remain available. But it's definitely worth hunting down, either the boot (which has pretty decent sound quality for a bootleg) or, preferably, the official release.
Here's an audio rip of "Gimme Shelter":