I started a thread about the most arrogant fans in football - clubs supported by insufferable tossers you just can't stand... but now let's look at the other side of the coin - the most decent. Not necessarily the clubs with the loudest support or whatever, but the clubs who are supported by mostly fair and decent people who make you think, "yeah they're alright actually".
Off the top of my head I'd say Arsenal fans fall into this category. OK, the gloryhunters are annoying, but the 'proper' fans seem OK. Remember when we beat them at the Emirates? A lot of their fans stayed at the end and gave our players a round of applause. Can't get more sporting and dignified than that. Also I recall that on their forums they actually gave us credit, a far-cry from the how pathetic Liverpool fans have reacted.
I seem to remember Everton fans being good as well.