I've got two and neither were because of anything good.
August 11, 1991 - Watkins Glen. This was back when I knew road racing was cool before the masses learned just how good it could be. My brother and I used to go to this race back in the late 80's into the early 90's, 1991 being the last time. It was a great weekend of racing leading up to Sunday's Cup race. My driver qualified in the top 10 and my brothers driver was starting P2. On that Sunday we were sitting in our usual location at the bottom of the hill in turn #2 leading up into the esses. It's not unusual that at the beginning of the race and after any restart that it normally takes the cars a while to complete the lap. This time though, just a handful of laps into the event, the cars didn't come back around. Sure enough the caution lights were on but unlike most cautions it was a red flag condition. Not able to be seen from our seat location was the end of the back stretch where there was a horrific wreck. Back then we didn't have scanners. Others may have but we didn't. We did have headsets that allowed us to pick up the radio broadcast of the race. On the radio not much was said other than who was involved in the accident. We knew by the amount of time that it was taking for track cleanup that it was something major. They seemed to indicate that it was due to catch fence repair. That was only part of it. We lost J.D. McDuffy that day. The backstretch of Watkins Glen was by far the fastest section of the track. It ended with about a 180 degree turn to the right. This was before the installation of the Bus Stop. I don't remember if it was brakes, a lost wheel or what but he and another car went straight through that turn and into the catch fence that was nothing more than tires and cable. He wasn't a superstar of the sport but he was a hard working, independent driver racing week after week. A fan favorite just because of his work ethic. He was the last driver killed during the actual Cup race until Dale Earnhardt lost his life 10 years later.
October 24, 2004 - Martinsville. My wife, kids and I were there for one of the many Martinsville races that we had attended up until that point. We camp about 20 minutes away from the track near Philpott Lake. That morning leaving the campground to head to the race, the weather was horrible. We weren't sure if they'd even get the race in. It wasn't long though that the weather was moving out and they got the race underway. After being subjected to another disappointing Jimmie Johnson win, we sat in our seats along the front stretch to watch the victory celebration at the start/finish line, a great tradition @ Martinsville. This time though instead of them holding a celebration Chad Knaus radioed to JJ that he didn't want him doing burnouts asking him to come to pit road instead. He pulled onto pit road near his teammates, which had also been stopped on pit road. It wasn't too much longer that we all started to hear about the HMS plane crash.
Two moments that I'll never forget while attending races. While there heave been many more great moments that I got to witness, those will probably always stand out the most to me. I hope I never get to add to that list.