Premium icon sharing site, FlatIcon, reduces prices by 40% for their summer 2018 sale. Though the site offers free service to all customers, unrequited attribution and other features are given to their premium subscribers. Instead of their usual $9.99/month or ($7.50/month if paid annually), the company is offering a low $5.99/month ($4.50/month annually). If you choose the later option, the total one-time payment comes out to $53.99 for an entire year of unlimited icon use and ad-free use.
I have used this site on a ton of different projects in recent years and they are by far my favorite icon distribution service. They have a handy search function that lets you find exactly what you’re looking for as well as the format you need – png, eps, svg, etc..
Additionally, there is a free Mac app that lets you browse their entire library and drag and drop any icon from the app directly onto your project canvas. The app does require a premium license as well, though a 10 day free trial is offered.