Discord, the insanely popular chat and VOIP client primarily aimed at gamers is now officially supported on Linux and out of beta.
Be sure to join our Discord channel to hook up with everyone: https://discord.gg/0rxBtcSOonvGzXr4
Download it here. It provides either a .deb or a .tar.gz and you need to be 64bit to use it.
Personally, I think it's great. You don't actually need a client to use it, as you can use it directly in the browser which makes it rather useful.
I've seen people worried about their terms and conditions, with it stating that by using it you grant rights to your content to the parent Company. To make it clear, this is no different to Reddit, Facebook and almost every site/application that you put content into.