As I mentioned yesterday, I got slightly obsessed with researching oscilloscope hacks yesterday, after seeing this jaw-dropping graphic demo released at Assembly 2007:
Digging around for oscilloscope art led me to one of the first video games (but not the first), William Higinbotham's Tennis for Two from 1958. Though it looks like Pong, its controls were more complex, letting the player set the force and trajectory of their stroke. Here's a simulator for Windows, if you want to try it yourself.
Since oscilloscopes are X-Y vector displays, it's not surprising that people have attempted to play classic vector games on their scopes. Moose hacked MAME to render frames as audio to the PC soundcard, letting him play Asteroids and Star Wars on his Cole S1001 scope.
Finally, this is more of an audio visualization of a software hack, but Mike Kan created a real-time visualization of a Mac OS booting up and accessing the filesystem and memory. Beautiful.
For more oscilloscope fun, see Phil Torrone's great roundup on Make, and related coverage. You can use freely-available software to make your own oscilloscope, or hack together one with a PIC controller, an old hard drive, or an old TV.
P.S. I typed this entry on an oscilloscope terminal.
February 15 Update: Inspired by this post, Matt Comi wrote a Ruby script called Oscillofy that turns any image into an oscilloscope-ready audio file.
February 14, 2011: NintendoScope plays GameBoy games on an oscilloscope.