I don't know that mine are necessarily weird, but I think they are interesting... anyway
My second concert ever, Metallica when I was sixteen, it was an open air place, stage is under an awning, lots of seats, and behind the seats is the lawn, anyway, I was in the seats. I got up to go get a water or something, and while I am heading over, there's a dude yelling at one of the security guys. I stand back, as there are other security guards moving towards the guy, and, I wanna see what happens. Anyway, the (obviously) drunk dude, just hauls off and punches one of the security guards. People had already backed up away from him, and the next thing I saw is a different security guards vault the fence and flying tackle the dude. It took four big ass guards to drag his ass out, which, in retrospect, means he was probably a bit more than just liquored up.
More recently, I saw something similar, at a GWAR concert in Washington DC, and I don't know what happened prior, but this chick was being thrown out, and while the security dude is walking behind her, she turns around and fucking decks him. Again, not the best thing in that type of situation, as that quickly brings other security guards to the spot, who are surprisingly gentle with her, and basically hold her put with her arms at her sides right in place, facing away from the stage until the cops show up like 5 or so minutes later.
The Zappa story reminded me of something a friend related to me recently (She works as a local stagehand / lighting tech / etc), and for the life of me, I cannot remember what band it was, someone with an expensive upright bass IIRC. Someone threw a half-full beer up on stage, which splashed all over the expensive instrument. The band quickly stopped, and brought up the house lights. The singer asked the crowd "Who threw that?" and apparently some drunk guy took total credit, jumping up and down and such. Guess where he went shortly thereafter?
The weirder things I see are going to things like Ozzfest, and seeing girls walk around in teeny tiny bikinis.... who shouldn't be. Why is it all the cute girls at metal shows are the ones in like, a long skirt and loose t-shirt, but the ugly, lumpy, missing half their teeth 40 year olds are the ones who walk around damn near naked attempting to make my eyes bleed out?