Toilet Paper Orientation
The debate over whether toilet paper should hang over or under the roll has sparked opinions on aesthetics, ease of use, cleanliness, and more. This issue was even discussed in a 1977 Ask Ann Landers column, which became one of her most popular topics. The "toilet paper orientation" debate is also used in sociology to teach social constructionism.
#6 Actually a really cool list
#19 I remember when I first found out that the Roman statues used to be paint to make them appear lifelike. Creepy.