Haha, some great 'moments' in this thread. I'll probably be repeating a few, but these are just since I've been supporting us (circa. 1998). These are my 'City defining' moments:
1. Losing to United not once, not twice, but three times in the last five minutes... in a single season.
2. Being 0-3 down away from home to Tottenham, down to 10-men, then staging the most unlikely comeback in cup history.
3. Being 4-0 down to Arsenal at home around abouts 2001 I think. The Arsenal team that day were playing some sublime football, us City fans came up with one of the best atmospheres ever that night. Such great chants as "We want five." Ole-ing the passes Arsenal were stringing together and making fun of David Seaman's pony tail.
4. Jamie Pollock scoring such a convincing own goal that you could have sworn he was playing for the opposition.
5. Stuart Pearce missing that penalty, the keeper told him he wouldn't try and save it. He just had to get it on target.