Other creative uses of ROM data? (Score 1)

I got a kick out of the use of bytes already in ROM as the map. I did something similar for an old DOS game of mine, Tunneler, where I used bytes taken from IBM PC ROM to replace the player's usual game view with a TV static/snow effect (simulated loss of signal). I grabbed bytes from an address in ROM that resulted in random-looking values interspersed with a few horizontal streaks. Know of any other games that made unusual use of ROM data?