I provide the number of the room next to mine when I have a very early wake-up call and the noise from the party in the neighboring room has kept me awake very late. Let them get their 3 hours of sleep!!

I use:
1. My watch -- very quiet
2. My Cell Phone -- a minute later. Louder
3. Room Clock -- If I can figure it out, set for a minute or 2 later.
4. Wake Up call -- Usually a half hour after watch alarm, the former being the time I REALLY need to be awake by (i.e. no cushion). Unless of course I've used the wake-up call on the annoying guest next door.