My first experience with CAD was creating models for my college senior design project. My project was an electronic version of the board game Clue(TM). There is an existing one on the market but it allows for only four players and I often ran into instances of having five to six people wanting to play.
I worked on understanding the game flow and creating my own version. Below is my design for my main enclosure that housed the bulk of the electronics along with storage for playing cards, envelopes, and player pieces off to the right. Did you have a senior design project in school? What did you choose to work on?