The BSOD ("Blue Screen of Death") screensaver that comes with xscreensaver is really creepy. The "Sorry, a system error occurred" dialog still produces that stomach-flipped-inside-out-and-is-eating-my-spleen feeling despite not seeing the real thing for years.
From a distance, the screensaver is quite convincing. Up close, however, there are a few details that need to be tweaked. First, the MacsBug screen needs to use the original Monaco 9pt font. Second, DOS and Linux screens need to use the 8x16 console font and use a dimmer color for the text.
BSOD has some undocumented, tweakable X resources that can be set, and the aforementioned fonts are freely available in PCF format. "ProFont for Linux/UNIX" can be downloaded from here and 8x16 is part of the "xfonts-konsole" package on Debian/Ubuntu. After installing them I added the following to my ".Xdefaults":
BSOD.Windows.font: -*-console-*-*-*-*-16-*-*-*-*-*-*-* BSOD.Windows.foreground: Grey90 BSOD.Mac.font: -*-profont-*-*-*-*-11-*-*-*-*-*-*-* BSOD.MacsBug.font: -*-profont-*-*-*-*-11-*-*-*-*-*-*-* BSOD.macX.font: -*-console-*-*-*-*-16-*-*-*-*-*-*-* BSOD.Linux.font: -*-console-*-*-*-*-16-*-*-*-*-*-*-* BSOD.Linux.foreground: Grey90 BSOD.SparcLinux.font: -*-console-*-*-*-*-16-*-*-*-*-*-*-* BSOD.SparcLinux.foreground: Grey90 BSOD.BSD.font: -*-console-*-*-*-*-16-*-*-*-*-*-*-* BSOD.MSDOS.font: -*-console-*-*-*-*-16-*-*-*-*-*-*-* BSOD.MSDOS.foreground: Grey90
Until now, the shrieks of terror from the thought of losing all of my work have been quiet. I can assure you that they are now quite audible.
(If you're having trouble getting it working, leave a comment.)