No one ever thinks about this, but when you're in a car all day, you're definitely feeling the blast of UV rays (especially if your car doesn't have tint). Plus, if you're driving by the beach, how do you not stop to jump in for a quick dip?
5. A multi-USB adapter
Your phone. Everyone else's phone. iPads. Miscellaneous other gadgetry. This little doohickey is a total lifesaver.
6. A phone or GPS mount
If you don't already have a mount in your car, it's absolutely essential. It'll give you easy access to the map and allow you to change up the playlist without diverting your attention from the road.