DMX512 is kinda cool. You often find it used in theatre. But these days it lurks in council public lighting systems and the occasional household Christmas display. DMX can control lights, fog machines, relays and my personal favorite, the DMX flame thrower.
When DMX512 was first developed in 1986, the original controllers were big, bulky and expensive. These days a Raspberry Pi can control DMX devices.
You will also need one of the following USB DMX controllers to go with your Raspberry Pi: