You don't need automation to use a transistor. Heck, you can find a use for them in nearly any project. I could easily imagine one being used
somewhere in a gameboy clone, but where exactly, I don't know. I'm currently working on building a temperature controlled fermentation chamber so I can improve my homebrewing, make lagers, etc. I cannibalized an old mini fridge, plus an Arduino Nano, a few relays, some transistors and a bit of code, and I can lager my beers during the middle of summer in southern California, and (hopefully) produce some very consistent ales. I'm looking forward to a nice, clean, crisp "lawnmower" beer for those hot days spent working in the yard or garage. Should be ready in a couple months.
EDIT: If you haven't been directed to it yet, there's a great site for electrical engineering info called
All About Circuits : Free Electric Circuits Textbooks.