Chimes of Death

This is the frightening and perhaps slightly satanic sound made by a macintosh with a serious error during power-on diagnostics or booting.

Ways to trigger this sound on purpose are to press the hardware interrupt switch (on very old models only) or to hit command-power immediately after power-on.

Some models of Power Macintosh also have a hideous digitized car crash sound, complete with breaking glass, that is played when serious errors arise during bootup. I'm not sure off the top of my head which ones, though; all I know is that it's a frightening thing to hear coming from a booting computer, especially since the Mac tends to play it at near-top volume...