Having more than one tool to do a specific operation so you don't have to break a setup. I don't have duplicate tools, but having a radial arm saw and shaper in addition to a cabinet saw largely means I do not have to break setups to crosscut something when I am set up for dadoing, ripping, rabbeting, etc. My shaper also has two spindles so I rarely have to break a setup on it either as I can generally use the "other" spindle.
I have a hunch that a HVLP spray setup would probably save me the most time as shooting lacquer would be grossly faster than brushing or wiping on varnish, but unfortunately I don't have such a setup...yet.