Similar to my previous question about Virtualization -- I'm extremely hard on hardware. I carry my machines around with me to class every day, and they are often shoved into a bag with various books, power bricks, and other assorted do-dads, and these things "press" on the top of the laptop case because in a laptop backpack the laptop is typically closest to your back. Therefore, I'm willing to spend some extra money to get a laptop that can take a beating -- because it's going to be taking it whether it can take it or not ;).
I've seen manufacturers advertise various different kinds of frame materials, I've seen them show various videos of their machines getting dropped, but given that every manufacturer seems to have a video of their competitors looking bad, I find it hard to use this as a comparison.
Also, it'd be helpful if whatever advice is given is obtainable via the Internet -- I'm not a fan of brick and mortar stores when it comes to things like laptops because I usually get them built with a non-factory-default configuration.
EDIT: I don't need something that's "military grade" or anything like that -- just something that won't develop problems for the use pattern I've described above. For example, I currently use a Dell Latitude E6500 and the LCD keeps developing bad spots.