Discord - Step up your game with a modern voice & text chat app. Crystal clear voice, multiple server and channel support, mobile apps, and more.
Linphone - Linphone is an internet phone or Voice Over IP phone (VoIP).
Mumble - Mumble is an open source, low-latency, high quality voice chat software primarily intended for use...
Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
Twitch - Twitch is one of the most prominent streaming services around, serving as a platform primarily for video game and pop culture streamers.
Sipdroid - Free and open-source SIP/VoIP Client