Many times while out riding you will be faced with a busted bicycle. And then it's time to look through your tool bag and see if you happen to have something along that will fix your problem.
Pliers! That's often the ticket, Broken shift cable? Tie one end to the frame, and use the pliers to put some tension on the cable and put the dereailer in the position you want. And what kind of pliers will you be wanting? Why locking pliers... which is why the Leatherman Crunch is my tool of choice.
Bent chain? Use the pliers to give it that 1/2 twist to straighten it out long enough to ride home. Comes with a philips screwdriver, standard screwdriver, file/metal saw, tiny screw driver bottle cap opener and of course a serrated blade for trimming those cable ties off.
Can't tell you the number of repairs I've used this tool for, but as I've always said, "how far are you willing to walk?" "Oh, well what tools would you need to ride the rest of the way to the bus stop/home?" And if your answer includes a pair of pliers, well consider the Leatherman Crunch. Expensive, yep, but well worth it.
Or you can wait until I ride by and flag me down, and I'll lend you mine.