It might have surfaced below the stairs, some conglomeration of mops brought together by the blood of a disgruntled janitor and the spirits of the hobos he loved. Maybe you have a killer mulch pile, with a seemingly insatiable appetite for troubled children (buy it, it's good damnit). Or, more notably, you have an iguana exposed to nuclear fallout who just so happens to have a taste for Asian architecture.
This may be a guilty pleasure of mine, but I love myself an obscure monster movie. Godzilla notwithstanding, the original creatures cooked up by supernatural forces have always been one of my favorite horror tropes. Done well, they can make the inane terrifying, and done poorly, it usually turns into a mess of hilarious crap. Some of my own early short stories could be categorized here. Not crap, but as monster stories.. Well, maybe crap too, shut up.
To any fan of Stephen King, this trope is usually recurring and satisfying. Killer cars, dead pets’ resurrected, entire houses; it all works for Sai King.
No matter who is doing the writing, there are a few things you can usually be sure of: if it exists, someone has probably twisted it into something else; Horrible snowmen, clowns, animals (usually made huge for effect), and dolls are the common culprits. Mimes could be considered part of this trope too, but only because they are such terrible, soulless, awful beings.
So, which objects-gone-rogue are your favorites? Have you ever written a story that meets this trope? If so, hit up the comments because I would like to know.