Besides Arduino projects, I also learned basic electronics and metal-cutting skills by building simple circuits into Altoids containers.
I started with Lady Ada’s Minty Boost, an iPhone charger that ran off two AA batteries in an Altoids Gum tin.
Then I built Make: magazine’s mini fume extractor that ran on two 9V batteries in a classic Altoids tin.
Finally I made two flashlights in Altoid’s Smalls tins. A button one from BrownDogGadget instructable and a magnetic version from DanielX’s instructable.
All of them still work more than ten years later.