TimeLeft - TimeLeft is a versatile desktop utility - it can be used as a countdown clock, reminder, clock...
Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
Dial - Quick & beautiful macOS timer.
wnr - Better than pomodoro, this timer app balances work and rest.
ChirpyTime - ChirpyTime: Timer / Alarm Clock / Clock app for iPhone / iPod Touch
Free Countdown Timer - Free Countdown Timer is a free, full-featured and user-friendly countdown timer for Windows