I rented an Audi from National Rental Car in June, and I bought the “loss/damage waiver.” They don’t look at the car at all when you drop it off. I also rented a Ford Focus in July through Enterprise with the same loss/damage waiver.
I travel a fair bit for work, and I highly recommend National. Better customer service and Enterprise has down-graded my orders in the past.
Most companies will accept a debit card, but if you don’t buy the loss/damage waiver, they will probably put a temporary hold on extra money to cover small damage (e.g. $200).