I think there are a lot of good ones. Packers of course. I went to a Chiefs game several years back, night game against the Bills (and not a great Bills team at that time). To this day, I still say it's the loudest stadium I've ever been to. We went last minute so we purchased standing room only. We walked around the stadium, couldn't find one empty seat anywhere. So I had a soft spot for them last year. Not this year of course.
Steelers fans, much like Eagles fans, seem to make their presence felt at every away game. Must be a state of Pennsylvania thing.
I think we can all agree though that the once proud Washington fans who made RFK shake like an earthquake are now nowhere near the top of the list. The type of thing that must make the lifetime fan and owner feel pretty good about the job he's done.