Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
Solvvy - Highly intelligent customer support self-service solution via AI/ML/NLP science
Zoho Desk - Industry's first context-aware Helpdesk Software
Whatfix - Whatfix Enterprise: Enhancing self-service capability of any web product
Salesforce Service Cloud - Service Cloud integrates customer service with social networks and provides a self-service customer portal and knowledge base system.
phpMyFAQ - phpMyFAQ is a world’s most popular mobile-friendly, feature-rich and open-sources FAQ software that uses PHP 5.