Do you have any tool that you use all the time? Do you recommend it to everyone unprompted? Is it ridiculously specific to your situation, wants and needs? Let every one know how they can make their sewing better!!
I myself don’t have any at the moment, but I have been eyeing a nice pair of left-handed fabrid scissors for quite some time and I might get it some day.
Rotary cutter and a cutting mat. Made cutting fabric so much easier, especially since my hands quickly get tired from using scissors.