I went to Glasgow last week, and stumbled across one that really ticked me off...
Rented from Budget (car provided by Avis for some odd reason), and the car had 3/4 of a tank of fuel. Duly, I went back to the hut and informed the chap. He said that the fuel gauge was faulty, and I had to keep the receipt when filling up the car to prove it had a full tank on return.
Not entirely happy, I asked him to write this down on my paperwork, which he duly did. I then headed to the nearest petrol station (1mile or so) and tried putting fuel in, which it happily took almost £10 worth (which in a fiesta sounds like a quarter of a tank) and the gauge went to full.
Headed back to the airport and queried this, to be told that as I drove out (less than 30 minutes before) they couldn't accept any queries.
Chalked it down to experience, but in future, I'm rejecting to drive any car with a "faulty fuel gauge"!
M.