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.
T-Clock Redux - T-Clock Redux in an enhanced fork of Stoic Joker's T-Clock 2010 with ISO week number support...
SnapTimer - SnapTimer is a simple, free, portable countdown timer for Windows.