Sabastian at Censtron has really outdone himself this time. He's the circuit bender who goes a bit further than messing up the samples on a Casio SK1 (his greatest hits included this and this). This time he's taken an old black & white TV set and turned it into a superpowered oscilloscope, which takes the input from a 1/4 inch jack and turns it into mad patterns. He's not overselling this thing when he says: "Words can not do this justice, watch the movie and see it for yourself, you will be amazed." I was. Product page with video.
Update: Turns out the system is called Wobblevision, and Here's how to build your own, but remember: "Do not go poking where danger might lurk."