osTicket - osTicket is a widely-used open source support ticket system.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
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
OpenRMA - Computer Repair Shop Software. Mobile Repair shop Software and any king of repair shop. Track computer, mobile, tv, jewelry, bike repairs and any king of repair shop.
HelpScout - Help Scout is a simple, straightforward way to provide excellent support
BusyBench - Computer repair shop software.