Alarmy - World's most annoying alarm app
Sleep as Android - Common alarm clocks ignore your sleep cycles, they wake you on schedule no matter your are currently in your deep sleep. Waking up from deep sleep is unpleasant, it makes you tired and it may negatively affect your productivity during the whole day.
Galarm - Social alarm clock and reminders
Free Alarm Clock - Free Alarm Clock is a free, full-featured and user-friendly computer alarm clock for Windows.
Barcode Alarm Clock - Alarm clock that won't stop ringing until you scan a barcode
Digital Clock 4 - Beautiful customizable clock with plugins