Design your own death knight

It's way too soon, of course, to know exactly what powers and abilities the death knights will have; the developers themselves haven't entirely decided. Only they know exactly what stage of the design process they're in, but today let's pretend that we ourselves are the designers, and now we're in the brainstorming stage of what the death knights are going to be like, how they're going to play, and how they're going to be different from other classes. What abilities would you give them and how would you balance them against the classes already available in the game?

While brainstorming ideas, keep in mind that players want the death knights to feel fresh and interesting, so they'll be wanting unique abilities other classes don't already have. At the same time, you can't make the death knight class overpowered in relation to all those other classes -- they will want to keep having fun, too, after all. So every ability you give the death knights has to have its counter in something other classes can do, like rock-scissors-paper. If you're feeling particularly professional this morning, you can go into detail about all these balance issues, or else you can just write the idea you think would be cool.