What it is One of the most confusing rental-car add-ons, insurance is optional in most states. Where mandatory, it's built into the basic cost.

What's so bad You probably don't need it. Most car insurance policies cover your rental. Some credit cards do, too.

Ouch! Collision damage costs $10 to $35 a day. You will also be barraged with options like personal accident or personal effects coverage at $3 to $6 a day, or supplemental liability insurance at $8 to $15 a day.

What you can do Check your existing policy or call your credit-card company to make sure you're comfortable with the coverage you have. Then ignore the sales pitch at the rental counter.