I enjoy working with electronics and building insect class battlebots!
One way to learn robust hardware design is to bring your creation to a fight and stress it to the breaking point. Strong mechanical design is obvious, but good circuit design can allow your bot to continue working through many faults, and possibly even win!
I like working with electronics and low level software. Reverse engineering circuits, fixing devices, and building robots is fun! I've been into building and competing with insect class battlebots for the past few years as well.