When renting a car at the airport, you are typically pressured to purchase insurance from the rental car company. The Columbus Dispatch has a very good article on what to look for, and what to avoid. My recommendation is to do your homework ahead of time and you can save a good deal of money.

When you rent a car, the scam you’re most likely to encounter is pressure to buy extra insurance.
Readers have asked whether sleazy rental agents target senior citizens. Not necessarily, but some agents do target renters who don’t know the ropes.
A basic rule is never to drive a rented car without two basic insurances: collision, which covers damage to the car you’re renting; and liability, which covers your financial responsibility if you hit someone else. Any other insurance you’re offered likely is to duplicate coverages.

The Columbus Dispatch - Travel.

Another outgrowth of the tremendous damage that the past two hurricane season have caused is the new policy by some rental car companies of holding the renters liable for damages on vehicles caused by natural causes. This is a change in policy that has not been widely announced, and should make a car renter prepared to check with their insurance companies to make sure you are covered.

Car-rental giant Hertz has changed its contracts to make customers responsible for damage from acts of nature.
It told its best customers last month that they’ll be responsible for auto damage from natural causes such as windstorms, hurricanes and tornadoes. In the past, it was the rental firm’s responsibility. Avis and Budget are moving in the same direction.
Hertz informed its #1 Club Gold members of the policy after quietly implementing it last year for the rest of its customers. Hertz says it’s not the first company to make the change, which it says was underway before Hurricane Katrina.

USATODAY.com - Car renters stuck with storm damage.