I’ve been using Todo.txt for a little while now. I love it for it’s minimalism. Simpletask is a more polished approach to Todo.txt. It has some nice additions like grouping tasks by project and more configurable widget. Simpletask on Play
Runners-up
Todo.txt
There is nothing wrong with this app, it just doesn’t have some of the niceties of Simpletask. You should gladly give Gina the $2 for coming up with Todo.txt.
Trello
While not what I’d pick for independent task management, Trello is great for collaboration. I use both Simpletask and Trello daily.