What’s your favorite QA tool that has saved you the most time, and why?

Being able to develop my own tools for testing, tailored to the needs of the project.

Other than that: Confluence / a business wiki

• being able to write down anything about testing (plan, note, report) in nearly any format (especial having lists and tables)
• can be easily shared with others
• you can edit pages collaboratively (at Jira the last one saving his changed description overwrites all parallel changes. No hint about other edits):
  • having multiple testers testing the same topic
  • using it for communication with developers: I have sometimes a table with a state column for the bugs I find at a ticket. Typical contents of the column are: to fix, to test, to discuss, OK, Won’t do

I haven’t tried it so far, but I really want to try TestCompass.