I have been using ManageEngine ServiceDesk Plus 8.0 for a quite a while now and really enjoyed it. Web based help desk software with integrated asset management, knowledge base, self service portal, and ITIL processes. Pretty good help desk software to implement and use.

I strongly recommend ManageEngine ServiceDesk Plus - Help Desk Software

For more information about product go to https://www.manageengine.com/products/service-desk/