Whats the weirdest concert you ever attended?

I have to say this is only bought up by one particular concert I attended in 1970 in Birmingham England.
I went to see a German band called Faust. They had a bit of a reputation for being more weird than most, and that's saying something given other bands around at the time and had an underground following along with Henry Pig and Hatfield and the North.
So.... I was in row two and eagerly waiting for the show to start. The auditorium was completely dark except for the lights on the amps. At each side of the stage there was a big old 36" colour TV set and a pinball machine.

In due course, everyone assumed that the band came on stage as the light on the amps went off in sequence as if someone was walking past them. Then, eventually, odd sounds started emanating from where we assumed the band was. Still no lights. Then the TV's burst into life and were showing a different channel on either side of the stage. Still no sign of the band.
Next a guy walks on stage in just his underpants (1970's Y fronts)and starts playing the pinball machine. Every time he used the flipper the TV channel changed.

This was how the whole one and a half hours were spent until the guy on the pinball either got bored or the band got bored but he just walked off, the music stopped and the lights on the amps flickered again so we assumed that the band had left the stage.

During the course of the "concert", there was all sorts of aromas of illicit substances. To put the icing on the cake, about half way through, a woman in the front row turned round to me and said "would you hold this for me" offering a newly lighted special cigarette. After passing it to me she proceeded to turn back to the front, lean on the stage, have very quick very rough sex doggy fashion with someone I can only assume was her partner and then ask me for her joint back!

My head was really messed up for weeks and I'm still not sure if it was the concert or the side show which was to blame.
July 2 1978? Willie Nelson 4th July picnic Arrowhead KCMO

Willie, Waylon, Jessi Colter, Jerry Jeff Walker and the Grateful Dead.

Cowboys and hippies, not a great combo
I would say Alice Cooper. I didn't even know who Alice Cooper was before going to the concert, could have been a chick for all I knew. In any case, a friend of a friend had an extra ticket and I went. Pretty bizarre show but the band was surprisingly quite good.
Tubegroover, I saw Alice around 1970 or so (in Tampa) and while he wasn't the weirdest I've seen, it ranks near the top for sure. It sure was the LOUDEST concert I've ever been to, my ears rang for a day after that show. Glad I haven't subjected my ears to too many aural assaults that loud.
- One Lou Reed concert I attended years ago, not outwardly bizarre, but this weird combination of 'eclectic' happenings between the perfomers and the crowd....
- Todd Rundgren's Utopia tour roudabout 1980, one particular concert in Western New York where I swear they were definitely in their own 'Private Idaho'....
- All time winner: Genitorturers during their "Alice Cooper meets Marquis de Sade phase...'
The last one and the most weird was with Gretchen Parlato(voice, marakas, hand-claps and beat-boxing) and Alan Hampton all instruments.
Normally Alan Hampton would play string double-bass, but he expanded himself to play other instruments: guitars and keyboards. Apparently, while Alan is descent bassist, he wasn't able to keep up with other instruments and made this concert truly messy. He wasn't able to catch the loop on the right key and on the right time and was often off the key in guitar and piano YAK!. Also I noticed he was sweating heavy and pale. This happens if dope was used. When you're on dope and trying to be useful, you need to 'catch' the moment when you're not in withdrawal pain, but not too high to be able to function. I guess Alan just got the dose right before performance and probably too big... Dealing with dope consumers is complicated indeed.