I was using the default alarm program for quite awhile. I had it set up to go off at 4:00AM while working some very early mornings. I installed Alarm Clock Xtreme to use some different options. Once ACX was installed the default alarm program disappeared from my app list, but the alarm icon stayed in the notification tray. Every once in a while my alarm still goes off at 4:00AM but I can't figure out how to disable!
I've uninstalled ACX and the alarm icon is still in the tray at the far right, next to the clock.