The high-lariously named BSODomizer is a little gadget that interfaces between a computer and monitor to display an image at either random intervals or when triggered by an IR remote control. The best use of this kind of toy, of course, is reminding Windows devotees like myself that the nerld-famous (nerd world) BSOD is always lurking around the corner, along with a Mac user who's waiting to screech "Get a Mac! Get a Mac!" like the most annoying parrot ever. The BSODomizer does have legitimate uses, like calibrating a screen, but flashing the BSOD without reason is definitely a more entertaining one. Besides, that pun would've gone to waste if it had been called the DIY Image Flasher or whatever. The BSODomizer is available from their website for $79 before shipping, and the site helpfully provides instructions for building your own.
Warning: the source link is NSFW if your workplace has a rule against ASCII drawings of Goatse. I wish I was kidding about that last part. [BSODomizer]