Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
Streaks - The to-do list that helps you form good habits.
Free Countdown Timer - Free Countdown Timer is a free, full-featured and user-friendly countdown timer for Windows
Taskful - Deadlines, meet your match.
SnapTimer - SnapTimer is a simple, free, portable countdown timer for Windows.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.