Quite a few college and high school athletic departments gyms use the Farmers walk, one hand or two. Either with a cemented tube with handles in it, DB or even a BB for better sports balance. Called suitcase walks also. Great going up a small hill. T-nation had an article about them a couple of weeks ago, which featured a trap/shrug bar if I remember correctly. Can also use a wheel barrel, which some guy's prefer. Also can go up hills that way.The weight doesn't rub against the legs.
Yes, is rare in regular BB'ing workouts. Great for the forearms, traps and the shoulder girdle. Also hips, abs and lower back. Warning I am going to use those over worked words, "The Core Muscles". That's where the Farmer Walk (or forms of) hits strongly.Think of it as a mobile DL, but easier to walk with. Just about works the same muscle structures. Good Luck.
Side Bar: We use to have a old medium sized refrigerator behind the gym. We would bear hug that and try walking around the backyard. Great for everything, including power in the upper body from the hugging and trying to keep it from falling as we walked. A lot of guy's got better chest and backs doing this. And surprise, stronger and bigger biceps. Guy's with shorter arms used a strap to help than with the frig. Hint: if you picked it up nearer the bottom, much easier to handle. Mostly the football played did these frig walks. Really helped with their game.