Atari Teenage Riot in 1998 at a festival. They were extremely loud during their set but when they were about to end they let their keyboardist shower the audience with an incredible onslaught of just digital noise. A pure, screeching, overdriven, chaotic cacophony that went on for quite a few minutes. I loved it. But as I felt my body bending backwards from the sheer power of the sound I noticed that maybe it´s a bit loud. Too late: For a few days I felt like I had pillows covering my ears, which, as it eventually went away, left a slight high-pitched tinnitus-beep that´s been with me ever since. I took it as a warning, I really like my hearing, and now I always put something in my ears.
Here´s a recording from a year later that gives you an idea of what happened there. I love how the it seems to start with a song only to descent into noise at 0:37.