I'm here to see how many people make their own apps for this :-) It feels like the cliche of both programming and time management to want to build a tailor-made system for tracking tasks, instead of just doing tasks.
I use a bunch
RememberTheMilk (RTM) as the real todo app.
Send myself emails for urgent stuff.
Google calendar only for appointments, I stopped using Google tasks because I wanted a single place and RTM was better.
Pocket for "reading" todos, i.e. articles I plan to read.
Google docs for organizing ideas.
Things written on paper if it's likely to be done within 1-2 weeks.
Joe's Goals for habit tracking sometimes (super simple).
In code, I leave todo's with my name (I have an autocomplete for that).
I did! I use cheq for quick little to-do lists, and since it saves the to-do items as JSON I have even built myself little HTML pages that can display the checklist in the browser as well, so I'm always able to quickly see the status of my 'cheqlist' at a glance :D