some of my favs that I can remember:
one of my rock bands playing at an outdoor festival thing, drunk guy comes up after our set to compliment us, goes up to the guitarist: "DUDE!! That was effin sick!! it was like you were playing..... SEVEN GUITARS!!!!!" then looks towards me, "you KNOW he's gettin some

"
at a recording session with the same band, engineer through the talk back mic says "thanks for not having sh*ty bass tone"
in college I was an education major and my main instrument was trumpet, but only ever played classical, never was good at jazz or "commercial/legit" stuff. I picked up bass while in college and it quickly became my primary instrument. I auditioned previously for the show choir band on trumpet but didn't get it (they wanted a screamer, which I was not lol). I auditioned on bass and got in years later. The band director gave me one of the best back handed compliments ever, something to the effect of, "you couldn't really hack in on the trumpet but sure are a great bass player" lol ummmm thanks?
More of a heckler, but playing an outdoor gig in Wyoming, this one guy keeps yelling at me "MORE BASS!!!" or "TURN UP DA BASS!!!!" and other stuff. My amp was maxed, there was a PA, and literally nothing I could do to turn it up, not that I would since levels were set fine by the engineer... until one of the subs caught fire. No clue what they did, wired something wrong or phantom power or something, no clue, but it started smoking so I heckled back at him, "see what happens when I turn up? The speaker catches fire!" This was also the same gig an older lady flashed me and the keyboard player...
one of my favs, drunk lady at a dive bar walks past us to go smoke as we finished a set, she tells us we're great, etc. She then looks at me and says, "and you're a killer bass player. And you're sexy AF. For reals" and walks off. I wasn't really sure how to respond to that as a. I'm married, and b. I've NEVER ever gotten a compliment or have anyone flirt with me at a gig haha. I was flattered even if it was just the alcohol talking.