A thoroughly annoying mobile phone ringtone. It sounds like a sort of musical warble, almost like a sparrow, followed by a loud, metallic bang. Not quite like a gunshot or explosion, more like the lid of a metal trash can being slammed. All I can think of when I hear it is some idiot chasing a sparrow around with a pot, and finally managing to catch it.
For some reason, this is almost as popular with the high school crowd where I'm at as the obnoxious near-ultrasonic ringtone. (The one that people over 30 supposedly can't hear. I'm almost 30, and I can hear it keenly, so can most of my friends, between 25 and 35!)