One that sticks out in my mind is an event my band were involved with, I will leave out the specifics as it is never classy to discuss specific venues etc.
Anyway we enquired about the event as we were interested in taking part and it turns out the venue has no amps, no pa, nothing so they asked us if we would lend our amps, pa etc for the event and our lead singer drafts up an agreement that they agree to in order to cover us in case anything happens to our equipment.
We got there and it turns out (though no-one explicitly tells us) that we are actually hosting this event.
Anyway first thing that happens, after the drumkit, guitar amps etc have been setup, our guitarist who knew full well that he was expected to bring my bass amp turns to me and says "Mark, where is your bass amp" the life drained from my face and after a few minutes of me refusing to plug into the pa he goes off and gets my amp and turns up with it about 10 mins later.
After everything is setup we start playing and I still don't to this day know exactly what went wrong but the 2 vocalists just could not get there vocals together, they fudge there timings, forget the lyrics and it is literally like they are both singing different songs from each other, during the break we have to calm our drummer down who is mortified and embarrassed to be there and is threatening to walk and just to add to my own embarrassment a couple of friends who had never been to any of our gigs before decided to come along to this event.
Fortunately after the break our singers got there sh!t together and we played well but by that point we had already made ourselves look like clowns