Accessory? It would have to be my SuperNova Chucks. After that the wolverine jigs for sharpening, then my monster hollowing rig, then my Nicols steady rest, then my CBN wheel from D-Way, then a steb center and a cone live center, then my vacuum chuck..........that is the descending order of priority in what was most important.............since gouges, etc are not counted in this.
of course, the safety things like air cleaner and Trend Airshield pro are key...........I consider those my health protection and not necessarily turning accessories,though they are used in turning sessions as well. I have not had enough time to use my rubber chucky reverse chucky thingy to be able to evaluate its value, but I think it will end up being an important accessory in my arsenal.
Remember, in a moments time, everything can change!
Vision - not just seeing what is, but seeing what can be!