It's really cool to see how many people shared the same experience!

In random order, and off the top of my head:

    - pong
    - some various demo where I would simulate fireworks or 
      traveling through star (in other words particles that are
      rendered by drawing dots and circles on screen)
    - a car racing game viewed from the top
    - an RPG engine but never actually made a level
    - a claw machine
    - and finally my own remake of space invader where you could
      play up to 4 in coop and upgrade your weapons. It had bosses
      and swarms of enemies. I learn then there was a limit of how
      many keys you can press on a keyboard before your computer starts beeping.