Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Service - Customer service issues solved for you, on demand, for free.
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
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.
LiveMessage from Salesforce - Make mobile messaging a cornerstone of customer service