Connecting 100k LEDs to a RPi is an interesting engineering challenge in its own right. (Also, if one LED consumes 10 mA / 30 mW, 100k will consume 1000 A / 3 kW.)
A more realistic thing would be a telnet chat server: code is dead simple, and the ability to handle NH / slashdot / reddit crowd on a RPi would indeed be impressive.
A more realistic thing would be a telnet chat server: code is dead simple, and the ability to handle NH / slashdot / reddit crowd on a RPi would indeed be impressive.