My previous personal project was a NES emulator. I thought it would be cool to use the Visibility Jam to program some features that provide visibility into the system. The ideas I had were:

• visualizing the CHR memory on a cartridge (basically showing the sprites used in the game)
• writing a disassembler, displaying 6502 assembly you can step through as the game runs
• nametable viewer (basically showing the backgrounds that the NES builds in memory, especially as the screen scrolls)
• memory viewer / editor
• wave form visualizer for the audio that the NES generates (NES has 2 square wave channels, a triangle wave, noise, and a channel for playing DPCM samples)