Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
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
Zoho Desk - Industry's first context-aware Helpdesk Software
ServiceNow - ServiceNow automates and manages global enterprise service relationships. Create a single system of record for enterprise services, automate manual tasks, consolidate legacy ITIL systems.