For car rentals (I've only rented in the US): definitely rent with the majors. Avis, Hertz, National, Thrifty, Alamo all have pretty good records with me, with Avis, Hertz, and National being preferred (I've never rented from Dollar). As stated above, the minors try to nail you for paint damage and dings.

Regarding Enterprise: I would advise everyone to avoid them. I had a similar situation to the one described above. This was in Seattle about 8-9 years ago at a neighborhood location. I had rented a car and hadn't checked the exterior carefully. I discovered in the car a rental agreement for a previous rental which described some (minor) damage on the passenger door. When I returned the car, they tried to hold me responsible and said it would be about $500 to repeair. For some reason, I decided to test them. I told them I knew I wasn't responsible for the damage. Not mentioning that I had a copy of someone else's prior rental agreement, I asked them if they could check previous rental agreements to see if someone else had noted the damage. They went into the office and pretended to do this and came back and said no one else had noted any damage. At this point, I brought out the rental agreement I had found and pointed out the damage had been noted previously. They were pretty nasty about the whole thing but I didn't pay anything extra.

A week or so later, a friend of mine from France decided to rent from them (I had tried to discourage this, but he wanted the great rate they offered - $9.99/day for a 3 day weekend). When he got there, they really pushed the "coverage" (insurance) - pressuring him for 30 minutes. I had warned him they would (they had tried this for about 5 minutes with me before I got nasty) and told him they could not legally require him to purchase anything. Nonetheless, he gave in and purchased the passenger liability coverage for about $4/day. Then, they told him that because he was from France, they'd have to run an authorization for the full value of the car on his credit card. When they tried this, it didn't work because he didn't have a credit line that high. They ended up running an $8000 preauthorization on his credit card (I never understood how they could do this and no one has ever tried that with me). If it had been me, I would have long walked away, but I guess since we had plans, he didn't do that.

I filed a complaint with the state of Washington and with the Seattle Better Business Bureau. Enterprise replied to the complaint saying that in the end, they hadn't charged me for the damage and my friend had agreed to the coverage and preauthorization, so they hadn't done anything wrong. As always is the case with the BBB (an almost worthless organization, in my opinion), this satisfied them and Enterprise wasn't left with a black mark on their record. There wasn't anything more I could do, other than never rent from Enterprise again, and to bad mouth them to everyone I could, which I have done since! Enterprise didn't seem at all concerned with the heavy-handed sales tactics, pressuring, and dishonesty of their Seattle location.