I keep an eye out for FC Köln and get over at least once a year but over recent years I've been going to a few Kaiserslautern home and away games and developed a bit of a soft spot for them after how far they've fallen and this season they look like they've got a decent chance of getting back to the 2nd tier. Some of their fans have a friendship with Kilmarnock fans from their time playing each other in Europe in the 90s, it's a bit weird seeing a load of Kilmarnock stuff on the walls of one of the fan pubs and a few banners in the terracing.
To be honest I've yet to have a bad experience at any German club including teams where the fans are meant to be either right wing or just have a reputation for being arseholes like BFC Dynamo, Dynamo Dresden or Hansa Rostock.