As a geologist, I usually have a magnet with me when doing field work. Of course, I also have two compasses and a GPS not to mention another compass in my survival kit, but still...

Even though I carry a magnet, I've never sat down with a needle and magnet to make a compass. This is an obvious gap in my education. For that matter, I also carry a couple of hand lenses and have never tried to start a fire with them. Time to get up to speed.