WARNING: THIS STICKER KILLS DEMONS!
As you may or may not have guessed I'm a fan of science fiction (I'd have to be to take the name of a certain time traveling alien as my own) as well as an afficionado of H.P. Lovecraft's C'thul'hu Mythos. Maybe I'm in dire need of calling the crew together for another tabletop RPG night or maybe I've been under a little too much stess recently but lately I've been on a Laundry Files bender. If you've never heard of Charles Stross he's an excellent author who writes this particular series, in which a halpless hacker named Bob was drafted into Her Majesty's Occult Service after writing a graphics hack that nearly summoned Nyarlathotep by accident. When not attending meetings or undergoing paperclip audits, on one of the charge codes on his timesheet he works as a computational demonologist. Another way of describing the series might be Delta Green meets Office Space.
Anyway, in The Laundry Files the character Dr. Monique O'Brien(-Howard?) obsessively carries a violin with a sticker that reads "THIS MACHINE KILLS DEMONS!" This is probably a riff on a sticker that Woody Guthrie had on his guitar which read "THIS MACHINE KILLS FASCISTS". I have a thing for redheads, and I have a thing for violin music (totally my jam), so I decided that I simply must have this sticker. I did some poking around on Cafepress and Zazzle but didn't find any, so I decided to make them myself.
Off I clicked to warninglabelgenerator.com (20151116: This site no longer exists. Bluh.), knocked together a couple of official-looking labels ("THIS MACHINE KILLS DEMONS" and "THIS LAPTOP KILLS DEMONS" (because Windbringer asked for one)), Googled a scalable vector graphic of the Elder Sign and found a suitable public domain version on a wiki. None of the warning label or sign generator sites I found had any Lovecraftian sigilae so I used the aforementioned graphic and The GIMP to make exactly what I wanted. I then pasted the images multiple times into 1200x1500 pixel full-sized sheets so there would be ten stickers each, the better to mass produce them.
Anyway, here they are: This machine kills demons! and This laptop kills demons!. Grab a package of inkjet sticker paper (I'm fond of Avery 3383), run off a sheet, cut them apart, and you're good to go.
Woody Guthrie came up with the idea. Many have riffed off of it over the years. I stole the idea from Charles Stross because I liked it so much. These images are for non-commerical use only, and if I find out anyone's been selling them I'll get really pissed off. Enjoy.
Oh, and if any violin players happen to put one of these stickers on your weapons of choice, please send Mr. Stross and I pictures, I think we'd love to see them.