probably done before, no doubt with a much punchier title, but hey.
I'll set the ball rolling.
Rearranging their furniture in their room at midnight.
Leaving the microwave door swung open when they're done with it time and time again.
Forgetting their key and ringing the doorbell to get let in at 4am.
Wandering around whistling and singing tunelessly to themselves every day.
Stealing your food/drinks, sometimes admitting they "borrowed" it and then never pay you back/'return' it, other times keeping quiet and hoping they got away with it.
Bringing people back to 'hang out' at 5am when you have work at 9am.
And so on....