What's the best briefcase for work?

I think the key for finding the best briefcase for work is to match the bag to what it's containing. For example, if you're just going to be carrying around a laptop and some magazines, the you can afford to be casual. They aren't the cheapest, but Tumi (http://www.tumi.com/) tends to make comfortable, computer-friendly nylon briefcases. On the other hand, if you're lugging around important documents, you'll probably wish to opt for a sleeker black leather briefcase with silver buckles. Consider Dunhill (http://www.dunhill.com/) which does a great job with this look.

Great response above. I just wanted to add that as a manager in the average modern corporate office setting, I dislike the briefcase strap which dresses down your appearance. I came across a great article detailing this concern about professionalism and briefcase straps here.