You would think that, by definition, a favorite tool would be a trusty one that you use all the time. My favorite tool is one that I have used only once and will probably never use again. It's a ratchet set where the sockets have the teeth on the OUTSIDE of the socket. I was trying to pull some EPA **** off a new motorcycle and had to take off the air injectors. They were just a bit taller than the deepest deep socket I could find. This set lets you stack socket after socket OVER the injector (or bolt, etc) as high as you want, then the handle fits over the last one and there you go. Kind of a poor description, but a great tool. My definition of a favorite tool is "the ONLY one that would do a specific job".
Mike