ToDoList is Free Open Source Software (FOSS) written in C++, see CodeProject article.
Ranked in these QuestionsQuestion Ranking
Pro Great functionality, lots of options
Cost, percent done, priority, you name it - you have it. If you prefer simple layout - no problem. You can configure everything.
Pro Configurable calendar view, day view, Gantt chart, Kanban
Pro Multi-level subtasks
Pro Comments with richtext format
It means comments can have different fonts, links to the pages or links to another tasks. You can format text your way.
Pro You can set as many filters as many columns you have, as well as export your view or single tasks
Pro Portable & lightweight
Default portable is 2.5 MB.
Pro Dummy content (optional) included
Makes it easy to comprehend most features.
Con Windows version startup too slow
8G RAM, SSD, ToDoList Starting always takes 3-5 seconds to load.
Con Android app is in early stages still
Only the Windows version is fully-featured. The Android app is still in early development.