At my first and only time renting a car, I was told that I was required by law to buy insurance covering damages. I did not know that I might have had insurance covering rentals elsewhere, even on credit card member benefits. I bought it for 20 something per day, and went outside to be presented a dented up car, whereupon I was told to not worry about dents since the car was already beat up.

On the plus side, I was also told the car only had a quarter tank full, but found a full tank. I didn't bother to report that, so I guess things evened out.