I taught a robotics class at a local high school and one of the projects that we invented for the students was a remote control Mario Kart balloon popping competition.
The students used a partially pre-made car kit, wired in transistors, batteries, and H-bridges and buttons and then wrote the Arduino code to control their kart. The competition was to see who could pop the opponents balloons first.
My brother and I decided to make our own R2-D2 robot after seeing the new Star Wars come out. We used an Arduino Uno for it’s brain, a servo to rotate the head, DC motors and an H-bridge, an LED, and a small 8-Ohm speaker so he could talk. This is the first iteration of our baby R2-D2.
Then I 3-D printed a model of R2-D2 and entered him in a 3-D printing competition.