qTox - A Qt graphical user interface for Tox.
Tox - Send messages, files, create groups and make Tox to Tox audio and video calls. Securely.
Toxic - Toxic is a client with an ncurses interface, written entirely in C.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
uTox - µTox is the lightweight client with minimal dependencies; it not only looks pretty, it runs...
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.