The Oakland Raiders, now of course the Las Vegas Raiders. I think it was something about their 'silver and black' colours that subliminally connected with my 'black and white' instincts. Only later did I learn about the global 'Raider Nation' and their reputation as the rowdy outlaws of the NFL, but it only reinforced my liking for them!
My only gripe is that the badge has become a bit of a fashion item and some people wearing it probably know next to nothing about the team or the sport, which makes it feel a bit too much like a worldwide corporate marketing exercise, but I'm sure the team isn't complaining about the global recognition and income!
In terms of success, the Raiders and Browns have had a lot in common for most of the past 20 years!