Man, I was renting an Avis car in Portland, Oregon while a renter in Portland, Maine wrecked her car. Avis sent me a bill for $2000 and refused to conduct a conversation with me for weeks on end. It turns out the reservation had gotten the Portlands mixed up, the Avis lot at PWM gave some woman a car with my info in it, then when she hit something they tagged me with the blame (the actual culprit/driver didn't complain obviously).

It took something like two months to straighten out, and I learned two things:

1) Routine Avis rentals usually run great, but as soon as anything goes even a little wrong, you're in hell.

2) There are a lot of functional idiots working at Avis corporate. I mean really, truly, the psychological/dictionary definition of idiot. I was driven half insane trying to make myself understood to these people.