irssi

An IRC Client. Command Line. Highly Customizable. Open. Free

A powerful communications suite for staying in touch with friends and family members

Chat with other people in a realistic environment

A feature-packed instant messaging client from a well-known email provider

A messaging app that uses WiFi to replicate traditional data plans for a fraction of the cost

Edit photos from a wide variety of sources using this tool kit that includes filters and stickers

Free and simple messaging app for Mac with a strong focus on privacy and security