Alarmy - World's most annoying alarm app
T-Clock Redux - T-Clock Redux in an enhanced fork of Stoic Joker's T-Clock 2010 with ISO week number support...
Wake N Shake Alarm Clock - Wake up with a jolt of energy ready to get shit done.
AlarmDJ - Online Alarm Clock - Use YouTube videos or MP3 files as alarm sound. Works offline.
Wakefy - Turn your Mac into a Spotify alarm clock.
DS Clock - Keep your time synchronized with Atomic Time servers, using customizable digital desktop clock with westminster chimes.