Taskful - Deadlines, meet your match.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Calendarist - Time blocking companion for Google Calendar
doo - A smart, simple app for reminders and to-dos
Gone - An ephemeral to-do list
Laverna - Laverna is a JavaScript note taking application with Markdown editor and encryption support.