Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
HelpStack - Open Source mobile help framework to support iOS and Android app users.
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
Chat Center - Chat with one click, no matter what messaging app you use
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
Helpshift - Helpshift is an in-game customer support platform that enables mobile apps to improve customer experience, drive higher ratings and increase retention.