The 20 most important tools ever

Here is the Forbes list.  Only hand-wielded tools count, so the knife is number one and the abacus is number two.  Number twenty is the chisel, leave further suggestions in the comments.  It is not politically correct to wonder about "the whip," but how would it fare on a pure utilitarian calculus, realizing of course it gets animals to do the work?  Maybe "the stone" is not sufficiently handmade, but how else did they cut umbilical cords?

Thanks to Eric and Kathleen for the pointers.