An Alarm Clock program for Commodore 64 that was originally published in C=-Lehti. This program is just about the coolest thing to get oneself awake with. It has all basic features (microsecond-precise clock display, snooze mode, screen blanking, no date though).
The music for this program was made by Jori Olkkonen. Of course, those who know a bit of 6510 assembler can change it to use any SID tune.