I currently don't use anything for
personal task tracking, since I am a part of a large team and we have project management. However, in college I explored this quite a bit. Here is what I would recommend:
* Text-based *
If this appeals to you, Taskpaper is a really good format with a lower barrier of entry than org-mode. There is a Taskpaper major mode for Emacs, a plugin for Vim, and even one for Sublime Text 2 (though the author didn't credit Taskpaper or Hog Bay except as "inspiration" at the bottom of the README): https://github.com/aziz/PlainTasks
* Simple but GUI *
Literally anything that allows you to create individual items, tag them (or add them to multiple named lists - same thing), and then filter by tag or list. Tags are all you need to implement anything from pure ad-hoc task management all the way up to strict GTD. Priorities are not essential and can actually get in the way; I've always found it much simpler and less of a mind burden to categorize tasks by project ("project" here meaning anything that takes more than one discrete task) and then simply tag the "Next Action" for any given project. You can then filter by "Next Action" and decide for yourself at any given moment what task will be best to do with the resources available to you (time, tools, location, energy).
Some examples of solutions that will do this:
- A directory of text files with #hashtags in their contents and grep
- Notational Velocity / Simplenote
- Any todo list app with real tags (not Wunderlist, for instance)
- Outlook
- Taskpaper or org-mode
I actually used Gmail for this for a while. I could expound on that if you're interested.
* The Full Monty *
OmniFocus, plus the book "Getting Things Done" by David Allen. It's cliche for a reason. It's not a silver bullet (obviously, I hope), but it is an effective system, it works for a lot of people, and you will probably get at least a few takeaways out of reading about it.