Discord is becoming the preferred voice chat for gaming. Given the amount of features it offers it is quickly replacing the long standing options of Teamspeak and Skype. Discord is secure and completely free to use with no gotchas. This means you can make as many servers as you want with no slot limitations. Not to mention not just a desktop application, but a voice chat app that works on your phone as well.
Discord channels are being used for all sorts of games and apps. One popular game using Discord is Tree of Savior and as a result we highly recommend that you checkout The TOS Discord gaming community.