Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Greenshot - Greenshot is a free and open source screenshot tool that allows annotation and highlighting using the built-in image editor.
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
Shutter - Shutter is a feature-rich screenshot program.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
MWSnap - MWSnap is basically a free to use Windows snapping tools that are used for snapping any part of the screen that is currently displaying on the front of all opened programs and windows.