St Pauli are my choice. Went to see them this season v Lubeck, and they were fantastic, it took me back to the way football used to be in the days before football became a corperate product. Over twenty two thousand for each game even though they now play in the Northern regional league in Germany. Plus they get over a thousand people to watch their reserve games and youth teams.
There not just a football club, their more like a movement, would defo recomend a trip to see St Pauli, more so if you like Punk and Ska music, cause you'll hear plenty of that in the pubs around the ground.