It is a pretty common first project to use an Arduino (or similar) to blink an LED. Which, of course, brings taunts of: you could have used a 555! You can, of course, also use any sort of oscillator, ...

Tetris is unquestionably a game for the ages. Despite its simplicity, someone, somewhere will always find a way to port the game (Translation) to just about any electronic device that can handle it.