Smart Sloth - Smart Sloth uses the concept of timeboxing, which is to allocate a set amount of time to each task, therefore, creating a deadline which can increase the productivity of the user.
ClocX - ClocX - freeware analog clock for Windows desktop with many features like calendar, alarms, skins, antialiasing and transparency.
TimeLeft - TimeLeft is a versatile desktop utility - it can be used as a countdown clock, reminder, clock...
LClock - Longhorn systray clock program
Dial - Quick & beautiful macOS timer.
DS Clock - Keep your time synchronized with Atomic Time servers, using customizable digital desktop clock with westminster chimes.