Discord

All-in-one voice and text chat for gamers

Discord is a proprietary freeware VoIP application designed for gaming communities. It runs on Windows, macOS, Android, iOS, Linux, and in a web browser. As of December 2017, there were about 87 million unique users of the software.

Reviews
Discussion
Hunter
Recently a group of friends and I have been playing Ark: Survival Evolved. We have been using Skype, but we have been disappointed in it's features, quality and performance while in game. Especially annoying things like whenever the person that started the group call leaves, the whole call ends and kicks everyone out. I was on reddit early today and saw an ad for this, and it seems pretty awesome. It looks like it is built on Slack somehow. Now just need to get all my friends to adopt.
I'm a huge fan of this product - my friends and I have recently switched to it from Mumble (and teamspeak before that).