Where to start....
I may be one of the unluckiest renter!
Hertz DC - Rented a Mercury Grand Marquis, drove to office car park and couldn't get out of the car, it locked me in. Climbed out of the window, which then shut itself leaving my luggage inside. Remote wouldn't open the car so had to call out recovery. Taken back to National Airport and given Lincoln (can't remember what type, but about size of Taurus). Now driving to Dewey beach on a nice warm day, so of course the car will switch on the heated seats and refuse to run the AC. So now diverted to Baltimore Airport where the rental agent told me this was the second car I had had in just one day! I thanked him for pointing that out. Wasn't the slightest bit sarcastic. He then gave me a Volvo XC70. That car was perfect.
Alamo Orlando - Rented a Trailblazer, rear glass fell out on 192. Rented a Olds Silhouette with the electric doors. Had to drive back to airport with them randomly opening and closing on the I4. Yes, to any other roaduser I was well aware of the gaping hole behind me!
Alamo Miami - Buick Century. Nuff said.
London, UK - Guy Salmon (remember them!) delivered an Opel Carlton to my office. My parking bay was number 4. Between bays 4 and 5 was an small area for motorbikes. Bordered by two concrete columns. So where did the delivery guy put the car? Wedged in between the two columns. He couldn't get out and we had to call the rescue services to drag the car out.