Here's a funny one. Happened to me and made me feel and look stupid, but is actually a classic:
Last night was the first studio rehearsal my band did for a gig we'll play in a couple of weeks, and the first time I played my Strat for real. Up to then I was only studying with it, mostly while sitting down on a stool in my practice room.
Everything was going just fine, until I began to notice that the overdrive wasn't as hard as I had set it to be. Then the drive and the sound began to be cleaner and cleaner until the guitar was mute.
Everyone stopped what they were doing, and we started testing everything, cables, amps, a lot of concern in finding out what was wrong.
Well everything was ok, and the logical conclusion was to tell me: "man, your brand new Fender Strat has a bad jack". Obviously a disappointment.
Happily, the studio had a luthier around. The guys took the guitar to him while I set up another one someone handed to me for the rest of the session, and in less than 5 minutes the luthier came in and said "hey man, there's nothing wrong with your axe, it plays ok".
Nobody understood a rat's arse, until it just came to my mind and I asked him if the volume was all the way down when the bandmates handed him the guitar. He said yes.
I figured that I was unwillingly touching the bloody volume knob as I picked, until it was all the way down.
Everyone laughed at me.
Fact is, I had never played a strat "live", standing and bashing the hell out of it before, only Sgs and Les Pauls so...
Ok, laugh at me too, you all
P.S. I edited the post because I forgot to mention: my tone was way better than with any other guitar I've ever played. The American Standard Strat is also by far the most comfortable guitar I've played so far.