Classy icons crafted according to Microsoft guidelines. Available in PNG and SVG. Free for a link
Sketch Confetti - Generate gorgeous confetti patterns in 1 click.
Feather Icons - Simply beautiful open source icons
Atomize - The most advanced Design System for Sketch
IconStore - Free icon packs by first-class designers
Merge Duplicate Symbols - Automatically find and act on duplicate symbols in Sketch
Flat Icons - 20,000 unique, customizable icons with free lifetime updates