I've used many todos during the years, but nothing really stuck.
The first I tried was Omnifocus, I liked it and used it for the good part of a year, but I found its many features way too much for me. I recently switched to Things, but I quickly found that living on your local machine you couldn't share your in progress todos with others.
The end solution is not pretty and it's splitted across multiple applications:
- Local Markdown Files
I use simple markdown files for most of my todos and for project management of smaller projects where you don't need to use the full functionalities of trello and a simple list of tasks is enough.
I use Trello to manage projects that are too big to be handled by a single markdown file, or for projects where I want to share the progress publically or with selected people (for example to my freelance clients so they can always see how the work is proceeding).
I use Wunderlist for shared tasks. It's in complexity in between the other 2 solutions. I can make multiple lists and decide to share some lists with another user
This is far from an ideal solution, I would love to just be able to use one single product instead of 3, but I still didn't find a single todo that does it properly.