Toggl - Toggl is an online time tracking tool. It features 1-click time tracking and helps you see where your time goes. Free and paid versions are available.
Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
Clockify - Simple and free time tracker. Perfect for small and mid-sized businesses as well as freelancers. Unlimited projects and users, unlimited productivity. Get all the premium functionalities, completely free.
SnapTimer - SnapTimer is a simple, free, portable countdown timer for Windows.
Cattr - Cattr is a free open-source self-hosted time tracker with desktop clients for windows, mac, linux.
Free Countdown Timer - Free Countdown Timer is a free, full-featured and user-friendly countdown timer for Windows