An example would be a power planer. I haven't seen a DeWalt cordless planer. And perhaps an AC-powered stapler; the cordless staplers are pretty wimpy.
I would love to see an inverter that accepts the DeWalt 18V battery and puts out 110VAC. Great for the occasional corded tool use without dragging out a long extension cord. Couldn't find any 18V-powered inverter on the Internet.