I thought I'd post an easy topic to keep the inclusive, nonspecific conversation going. What's your favorite lathe tool and why?
Here's mine for the week. The Jacobs Flex Collet Chuck. It's been living on my spindle most of the time in the couple years since I bought it, which surprises me. It offers good support and dialed-knutz centering throughout its capacity. It's in a different class entirely when it comes to work support than ER or 5C. It is non-marring. It's easy to pop out and swap collets. When I need a true 4-jaw, or big support of a 3-jaw, or inside jaws, then the right chuck comes out, but I really like the precision and repeatability of the flex collets.
What's yours?