Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
TIMEBOX - An advanced timer for professional meeting facilitators
SnapTimer - SnapTimer is a simple, free, portable countdown timer for Windows.
MetaClock.com - MetaClock is an Online Alarm Clock that can play YouTube videos and uploaded MP3s as an alarm tune. It supports Chromecast which means you can turn your TV or stereo system into an alarm clock. No installation is needed, it can also work offline.
wnr - Better than pomodoro, this timer app balances work and rest.
KukuKlok - Kukuklok is a free alarm clock available online and offline.