My wife no longer uses an alarm clock, since she works nights and sleeps when she can. We NEVER wake her when she's down!
... but she has an alarm clock that sounds like a dumptruck backing over your head. It works. You will wake the Hell up.
I always set an alarm clock if I have to get going early, but I always awaken before the alarm. Always have. Don't know why.
Used to be because of my sweet cat, but she's gone now. I can't imagine how that cat could tell time so well, but she always licked me awake at my eyelids a few minutes before the alarm went off. How did she know?
I miss her.