Love taskwarrior. As someone with ADHD/executive function issues, who struggles to prioritise, I find the "urgency" calculation invaluable. Even when it doesn't quite match reality, it's handy to have a starting point I can disagree with.

The extensibility is fantastic. I have little cron scripts to pull my work tasks from Asana, requests for code review from Github, and enter a task automatically when someone on my team requests leave for me to review.