There's so many to choose from and all the above are notable - although I don't remember the ECWC game being pulled but remain disappointed to this day that it wasn't shown live.
Wolves was my first Wembley trip and that offset the disappointment of actually losing.
Luton wins it for me though: that was a horrible shock. My first experience of relegation and something that I never expected to witness.
The latter stages of the Gillingham and QPR games were bad but fleeting moments of pain wiped away by unadulterated joy but in both cases, I it was more a case of numbness and a fear of the real pain that could come but that, for some reason, I never completely believed would. With Luton, it was a case of worst fears realised. By the time we got to Stoke away, I was too used to the worst happening.
edit.
Actually my worst footballing moment was having someone dislocate and break my ankle in three places a few minutes before the end of a game at Hough End. I couldn't look at my own foot sticking out at an unnatural angle. I had to wait about 30 minutes for the ambulance to arrive and essentially take me across the road to Withington. Once the adrenaline wore off, the pain was baaaad and the relief of the gas and air the ambulance guys gave me a huge relief. Unfortunately, as I'd eaten breakfast, they had to wait four hours before I could have a GA and they could operate so I had another period of extreme pain just before they put me under as I couldn't have any more pain medication at that point.