QOwnNotes - QOwnNotes is a free plain-text notepad with markdown support for Linux, Mac OS X and Windows, that works together with ownCloud Notes.

Todoist - Todoist is a to-do list that helps you get organized, at work and in life.

Go For It - Go For It! is a simple and stylish productivity app, featuring a to-do list, merged with a timer that keeps your focus on the current task.

Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.

Todour - Todour is an application for handling todo.

Sleek - Eliminating Physical Lines Forever. No apps & No signups 🙌