I have two answers to this:
As a neutral (not a Liverpool fan at all), I can't look past Gerrard's two last minute saviours for Liverpool - against Olympiakos to keep them in the Champions League the year they won it, and his last second half-volley to tie the FA Cup final up at 3-3. What I love about both is that they seemed almost cornilly scripted and I love it when commentators genuinely lose the plot and just get over-excited. Pure emotion.
Olympiakos:
http://www.youtube.com/watch?v=JUq7_rzXkEc (there are better quality links, but others cut the commentary short).
West Ham:
http://www.youtube.com/watch?v=vXrkDeNxGcM
On a more personal level, as a Huddersfield Town fan I'd pick the away win at Manchester City just over ten years ago. We were both mired at the bottom of what is now The Championship (remember those days, City fans?). We staged an incredible recovery mission that season and stayed up on the back of appointing a popular ex club captain as manager. City went down to the third tier of English football. I went to the game in Manchester, my only ever trip to the old Maine Road stadium and we walked through Moss Side (one of the roughest housing estates in the country) in Huddersfield shirts, bricking it (poor choice of car park!).
One of the classiest goals I've seen in the flesh - a 16 pass move, involving 7 different players, finished by a first time volley. A thing of beauty.
http://www.youtube.com/watch?v=7WBzcBggcbE
It was made even better as it was our first away trip to Manchester City for over a decade. Last time, we'd been beaten 10-1, the only occasion in English League History (125 years) that three hattricks had been scored in a league game.