Hanken Grotesk is better known by its former name — HK Grotesk. It was renamed Hanken Grotesk because it’s pending approval in the Google Fonts Directory.
It includes no less than 10 styles: 5 weights (Light, regular, Medium, SemiBold, Bold) with matching italics. It’s one of the best free font families ever made, and it’s 100% free for both personal and commercial use.
Update 20 Feb 2019 New weight! Hanken Grotesk Black