Nails scraping down a blackboard sends a shiver down some people's spine. For some people, it is the feel of cotton wool against their skin, and for others, two pieces of polystyrene rubbing together. What does it for you? For me, it happens when a piece of wet, unfinished wood touches my tongue/lips. You might ask - when the hell do you put pieces of wet, unfinished wood in your mouth? The answer? Lolly/popsicle sticks. I am always really careful eating them to avoid letting the stick touch the inside of my mouth.