HelpScout - Help Scout is a simple, straightforward way to provide excellent support

Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates

Zendesk - Zendesk is a beautiful, lightweight help-desk solution.

Crisp Chat - Multi-channel customer support software

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

Helpy.io - Helpy is a tightly integrated customer support platform that combines ticketing, knowledge base, community and AI support chat.