Twice, both times in my bygone youth, I've had Enterprise add insurance after I said no to insurance. One of those times, I caught it on the way out. The rentbot said he was trying to help me out by adding the insurance. The second time, I only caught it when returning the car. The insurance charge was removed when I threatened to call the police (of course, the police aren't in the business of adjudicating civil disputes, but how would the mouthbreather behind the counter know that?).

I also enjoy the creepy and persistent interrogation about what I'm doing in [city], and where I'll be driving the car.

That said, they are sometimes a good deal on weekdays, and I like the free bottle of water.