XO Hosted PBX - Hosted PBX is a scalable UC solution that uses cloud technology to integrate HD voice & data services, mobility, along with advanced calling
Dialpad - Switch is a cloud-based phone system built for Google Apps users.
Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
Genesys Cloud - As the foundation of great customer experience, the Genesys PureCloud contact center platform empowers your business to provide excellent service across the entire customer journey.
Sipdroid - Free and open-source SIP/VoIP Client
8x8 X Series - X Series connects teams across channels and around the globe, giving you access your most critical information securely, from any location.