QKSMS - QKSMS is a beautiful communication app that offers magical texting experience.
KDE Connect - Integrate Android with the KDE Desktop
Messages by Google - Messaging and SMS app bundled in stock Android.
Pulse SMS - Pulse SMS is a next-generation SMS and MMS application that is fast, secure and packed with lots of modern features as well as customization feature you cloud want.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Handcent SMS - Handcent SMS is a free enhanced SMS and MMS application for Android.