If you define "gig" as playing on a real stage, in front of more strangers than people we knew......
The year after I graduated High School I hooked up with a drummer who was one of my best childhood friends and we started jamming with a guitar player he knew. We'd been playing together for a month or two as a LOUD three-piece ala Hendrix, Cream, etc. and getting reasonably good at it, when our "Big Break" hit us like a ton of bricks - opening up the talent show at the Central High School in town (almost 4000 students strong). The drummer was a Senior at the school and he's the one that scored the gig
So, to set the scene.......
A beautiful old school auditorium that could seat roughly 1000 people, better than half full
We had the opening slot, to be followed by the absolutely blazin' HS Jazz Band: all top-notch players for their age, about 10 guys in the horn section alone, hard-driving rhythm section, led by a local Jazz player who taught there (Gigi Gryce's brother Tom, in case anybody's interested). These guys were playing Buddy Rich style charts and absolutely
nailing the material. A take-no-prisoners Big Band that was led by a Master, and tighter than a nun's *ahem* well, you get the picture.....
I was playing my brand-new fretless P-Bass through an Acoustic 136, the guitar player was using a Les Paul copy of some sort through a 50watt 2x12 amp, drummer with a respectable kit but nothing fancy. No PA, of course (this was about 1978 and we were instrumental only)
With little gear to speak of, we set up quickly in front of the Stage band and did a 5 second sound-check that sounded
nothing like it did when we were playing in the basement, and then dead silence......
I took a quick look behind me at the Stage Band eyeing us up from behind, then turned back around to see what seemed like a sea of black faces staring at the only white boy in the entire hall - Me (the guitar player and the drummer were black) - and we damned sure didn't look like the kind of band that was gonna be playing any James Brown tunes
Nowhere to run to now
I pegged both knobs on the fretless (the Acoustic was already maxed) and hit my big opener to the first tune - a big 4-note E7+9 chord with the top three done in harmonics and the low E ringing, that set up the intro lick to Purple Haze
And this voice shouts out from the middle of the crowd
Yo! Check it out! Led Zeppelin y'all !!!
That broke up the entire crowd and everybody on stage too, all of us just about pi**ing our pants from laughing. A couple of seconds to recover and it was take-two of the big E7+9, then right into the best facsimile of the Experience that three green kids could've possibly pulled off
Finally, the last note of guitar feedback fades off into the depths of that cavernous hall, then a couple of seconds of total silence.....
Followed by honest applause and even a cheer or two

I've been hooked ever since
Oh, and as you would expect, the Stage Band then proceeded to wipe the floor with us LOL