According to the NY Daily News, New York Giants running back Brandon Jacobs, who is slated to be starting this week, was fined $20,000 for "unsportsmanlike behavior towards fans". The article states that a league security representative caught Jacobs "making obscene gestures and yelling obscenities towards fans" before the Giants' loss to the Philadelphia Eagles last Sunday night. Of course, this would be the second time this season that Jacobs has been fined this season, as he was fined $10K for throwing his helmet into the stands during their road game at Indianapolis.
However, it may not be the first time he has gotten into it with fans during pregame warmups at Philadelphia. Youtube appears to have a couple videos, such as this one, which were taken at Philadelphia during last year's Eagles-Giants game which clearly show Brandon Jacobs getting into it with Eagles fans.
This one claims to show Jacobs cursing at the fans, although it is hard to hear him over the Eagles fans themselves, and arguably their language is worse than his. Some Eagles fans need to wash their mouths out with soap.
I'm guessing that since Brandon Jacobs wasn't fined for his behavior before last year's game against the Eagles, he must have stepped it up a notch this year. Still looking for footage from this year's pregame warmups, so if we find it, we'll be sure to update this post.