Several of the larger Swiss Army knives from Victorinox include a combination metal saw and metal file. This tool has a file on the two faces, and sharp saw teeth along one edge. The file compares well with regular flat files, although it is smaller, of course. When new, the metal saw is almost as sharp as a hacksaw blade, although it is much thicker, and will take longer to make a cut.
Uses: If you use the metal saw or metal file frequently, this is probably the first tool that will become dull on your Swiss Army knife.
Unfortunately, it is difficult to sharpen the saw and almost impossible to sharpen the file, so you might want to reserve them for emergency use, for soft materials, or for times when it's the "just right" tool (for example, cutting a nail or bolt that you can't reach with a regular hack saw.)
You can also use this implement as a nail file.