Select Similar Layers - Sketch plugin to select layers with the same attributes
Base UI Sketch Framework - Huge set of everything you need to design and prototype
Framer Inventory 3 for Sketch - Import states & export prototypes from Sketch to Framer
INSTAD.IO - Automagically converts vector images into sketchy style
UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.
Sketch Extensions - An official collection of Sketch extensions & plugins