If you are a US resident, purchasing Loss Damage Waiver from the car rental company is optional. Some customers choose not to purchase any protection products because they are covered by their personal insurance.
Renters are responsible for the full value of the car in some states, plus expenses for towing, administration and loss of use. Laws are different in California and Nevada, where renters financial liability related to vandalism is limited to a certain amount.
Car rental companies offer Loss Damage Waiver as an optional protection product which relieves the renter of all financial liability for any damage caused to the vehicle. However, this is only valid if you have not broken the terms and conditions of the rental agreement. The cost of Loss Damage Waiver varies based on which supplier you are renting with and which location you are picking up the car from.
Read more about picking up a rental car in the United States.