I've seen *a lot* of Phish shows. So of them, the best individual show I've seen I'd probably give the nod to November 2nd, 1996. You see, two nights prior Phish were joined on stage by Santana's percussionist, Karl Perazzo for their Halloween "musical" costume in Atlanta, GA where they played The Talking Heads' "Remain in Light" LP in its entirety. If you're familiar with that LP, they needed a percussionist in addition to their standard rhythm section. Anyway, Karl stayed on for the following two dates in Florida (West Palm, and then back up to Gainesville).
I saw both of those shows, but the one at Coral Sky Amphitheater in West Palm Beach takes the cake.
Other shows of note:
The Stone Roses up at Madison Square Garden back in the summer of 2016 was amazing.
Courtney Barnett, The National, and The War on Drugs all put on memorable shows at the Shaky Knees Festival down in Atlanta in 2018.
Wilco (another band I've seen often) at their Solid Sound Festival back in 2017 opened their time slot on the first evening by playing the album, "Being There" in its entirety (this was fan-voted beforehand). For the encore, they decided to play the runners-up in the fan vote, "Yankee Hotel Foxtrot,", also in its entirety.
I saw The Tower of Power at the House of Blues in New Orleans back in 2011. Great time. Dr. John came out for a bit that night, and the spotlight shined on none-other-than Allan Toussaint who was in the balcony.
I caught Iron Maiden's Seventh Son of a Seventh Son tour down at the Hollywood Sportatorium in Florida. What was that? 1987? 88? I also caught the Def Leppard Hysteria tour over the holidays at the same venue, and their opening band, Tesla, blew them off the stage. That was the Mechanical Resonance tour. Another show I saw where the opening act completely upstaged the main event was when Soundgarden opened for Guns-n-Roses 12/31/91 at Joe Robbie Stadium down in Miami.
Lots of shows....I caught Blind Melon at USF (free show) before they hit it big. Holy crap were they good. That ticket also featured the headliner, Kevn Kinney's Drivin' n Cryin' on their "Fly Me Courageous" tour. Technically Blind Melon opened, but Drivin' n Cryin' brought the same amount of energy.
Damn - that was free, too.