Check your insurance
Pros: The rental guy "had never heard of" the rental insurance I bought through Kayak (which was apparently a lot less expensive than Enterprise, but make sure you have other liability insurance). He also swore that I should have been aware of other costs and identification associated with using a debit card, although my first hint was at the counter. After that was all handled, everything was wonderful, but those were really unwelcome things to have to deal with on the spot.
Cons: Extra income proof for debit card, extra deposit for debit card, general clueless Ness of counter guy.