If there is one thing that I don't want going bump in the night, it'd be a harp. Sure they may look all fancy and try to lure you in with the strings, but when those things fall, LOOK OUT.
Another thing that is most annoying to go bump in the night is a hive of bees. They are quite loud, and manage to fly into your nose and sting your brain. That is never fun, especially when you're trying to get some sleep.