Best Practical Request Tracker (RT)
RT: Request Tracker is a battle-tested issue tracking system which thousands of organizations use for bug tracking, help desk ticketing, customer service, workflow processes, change management, network operations, youth counselling and even more. Organizations around the world have been running smoothly thanks to RT for over 10 years.
RT is also used by SFU's Help Desk. Documentation for our version, 3.8, can be found here:
https://www.bestpractical.com/docs/rt/3.8/