aTalk - An encrypted instant messaging with video call and GPS features for android.
FluffyChat - Open. Nonprofit. Cute ?
Talk360 - Talk360 is a best-in-class communication utility that offers a convenient way to connect with loved ones globally.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Molly (Signal fork) - Molly is an independent Signal fork for Android
TeleGuard - TeleGuard is a secure messenger that makes it store that your data or chats are not stored while collaborating or communicating with partners and friends.