Turned up at a gig, set everything up except the guitar which I left until the very last moment. When I did go to set it up i found ... an old, broken bass from years back staring up at me from inside the case. My wife had been helpful and tidied a few things up for me. Aaaargh.
Stupidest gear related thing I ever did though, was a result of my drinking (I don't any more). We'd done a gig at Swindon Town FC's function room and I woke up in the car in their car park the next morning. The first team getting onto their coach for an away fixture must have woken me. As I drove (yes probably over the limit) out of the car park I had to stop and pick up bits of my kit which marked a trail back to the door of the function room. Including my brand new Shure wireless rig in it's case.
Miracle everything was still there not nicked or run over, I must have been dropping stuff, falling over wandering around pissed up.
I don't need to tell anyone the moral here do I?