Snarl - Snarl is a notification system for Windows.
Zoom - Equip your team with tools designed to collaborate, connect, and engage with teammates and customers, no matter where you’re located, all in one platform.
Notifu - Notifu, a free open source pop-up balloon utility
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Notify OSD - Canonicals on-screen-display notification agent, implementing the freedesktop.
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.