Halp - Slack-first ticketing for internal helpdesk
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
HelpScout - Help Scout is a simple, straightforward way to provide excellent support
HelpDocs - Educate your users with a super simple knowledge base that’s built for teams just like yours.
ProProfs Help Desk - Help Desk software by ProProfs to help support agents track, prioritize & resolve customer support tickets. ProProfs Helpdesk makes you more productive.
phpMyFAQ - phpMyFAQ is a world’s most popular mobile-friendly, feature-rich and open-sources FAQ software that uses PHP 5.