You probably have an adjustable wrench in your tool box.
Have you ever used it so much your thumb would get marks from turning the knurled wheel?
Well the Crescent Rapid Slide made by Cooper Hand Tools removes the slow knurled wheel and replaced it with a slider mechanism. It was named in the November issue of Popular Mechanics as a one of the "Breakthroughs of 2006."
The only problem I could see is if the slider was positioned in the middle of the handle, it could hinder getting a good grip on the wrench.