It is not the loudness, or irritating-ness of the alarm (both can be tweaked slightly by choosing a suitably annoying song like Daft Punk’s (Like It, Do it) Work It) that makes an alarm effective, but the vigor in which it persists in ringing – no matter how many times you snooze it, when in fact you actually meant to kill the damned thing, forever.
The best alarm, imho, works against your basic motives.
And for all of the above, the BB is incredible. I use this ringtone which is so bad, it drove everyone insane when it kept shrieking wildly at 5am when we were in Phuket. Shrieking tones are largely effective.