Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Clara - Clara is a virtual employee that schedules your meetings, getting you to the work that matters, faster.
Raiseaticket - Raiseaticket is a 100% free cloud based helpdesk for customer service and support. The saas provides portal, workflows, insights to manage communications for the support and service process.
Mia - Virtual assistant for meetings
Best Support System - Best Support System is self-hosted support ticket application.It handle support ticket, manage email ticket, collect any payment by paypal.
x.ai - x.ai is a tool to schedule meetings for you and your team.