The face of pure disgust and disbelief your Mum (or any other member of you family or friends who is full of pride when it comes to furniture) make when you place a drink down on any special or expensive piece of furniture without a coaster underneath it.
Son: *puts coffee down on coffee table without a coaster*
Mum: Oh! *makes lackocoaster face* What is wrong with you!? There is an extreme lack of coaster-using in this house! That will stain!
Son: Ok Mum! calm down, there's no need to make your lackocoaster face!