I used to have nightmares about our furnace turning into some kind of monster. I would be next to it in the furnace/laundry room and would yell at it to stay away and it would come to life and roar back at me. I think it's because I was used to hearing the thing switch on and off, since the room I shared with my brother was in the basement across the hall from it. It's all kind of weird because my dad to this day is a furnace repair/installation mechanic (my brother is now too).
I'd also have nightmares of construction machinery getting a life of their own and chasing me, like something out of
Maximum Overdrive. At around the time the movie came out (1986), I was ten years old and living in a new subdivision, and so I was used to seeing dump trucks, dozers, and excavators rumbling around the neighbourhood. In the dream, I would be riding my bike and they'd come to life and chase me.