I mostly print tabletop RPG terrain elements, to bring some depth to my games. Also, because small objects don't require as much of a time commitment to print. My previous printer was prone to failure, and I downsized on my current printer partly because I pretty much only printed small objects anyway.
I've started expanding a bit into making some things that are either useful to me or can be used on various projects. At the time of writing, I am installing a Raspberry Pi into the case of a Rockband 3 keytar controller with a wireless computer keyboard in place of the piano keyboard. This is requiring me to design custom components for the case and to find appropriate items to remix for interesting details.