I'm kind of with Maglor on this one.
Even though Batman Begins kind of failed building up Scarecrow as nothing more than a putz, for a split second, when he comes in, straight jacket with mask, horse blazing, you get that feeling that, there he is, SCARECROW. I didn't expect a full fight between him and Batman at the climax (that was meant for Ras obviously) but it was disappointing that Scarecrow didn't get to have a final run in with Batman. Though, they made up for it in TDK I guess, but at the time we didn't know he'd be back and getting tazed by Rachel sucked.
It's more iconic than yet another business suit with shirt and tie, this guy was just let loose from Arkham, drugged on his own fear toxin. The tattered straight jacket is closer to the comic book and Scarecrowesque look than simply Crane's old dress clothes from when he went to Gotham University.