Also Hawaii - Maui, specifically. Rented from one of those local places that advertise all over the internet - well maintained used cars, off airport so you don’t have to pay all those fees, etc. All pretty much worked as advertised, except for the well maintained part. We had a Nissan Frontier that was downright sketchy. Tires were almost bald (it rains on Maui, so that can be a bit of a problem...), and of course they were non-matching. Shocks were blown, power steering pump was singing arias, there were loose trim pieces dangling into the front wheel well leading to loud noises if you turned the wheel at any significant angle, transmission was jerky, brakes were wobbly and faded so fast you constantly wondered whether you’d come to a halt if you needed to.

But that wasn’t the worst rental car experience I ever had - that would have been a fully routine big company rental (Hertz I think) in the mid-90s. The car started out fine (non-descript Chevy mid size sedan). Picked it up at the New Orleans airport in fine condition (well, other than being a mid-90s Chevy...). The problem was that I was on a consulting gig, and one evening I gave two other consultants from my same company a ride to New Orleans (we were stuck on a rather dreary compliance audit project about an hour away). I met up for dinner with a friend, while those two went out exploring. Picked them up later - and one of them was getting seriously green after having obviously too much to drink. Couldn’t pull over quickly enough for her to get out, so she ended up puking all over the backseat. She spent much of the next morning before breakfast cleaning out the back of the car, but with that nasty velour upholstery and the Louisiana heat, it was a losing battle. Drove the thing for a few more days with open windows and the A/C cranked. Returned it after hours at the airport on the way back, never heard about it. I’m guessing that car turned into one of those sketchy ones, where people would rent it for however long it stayed in service afterwards and notice a faint smell of something rather nasty.