These things you will not use often, but when you need them, you’ll be glad you have them.
First, get a trunk organizer. These vary in price from $25 - $50 depending on your needs. This one should do the trick.
One of those fluffy dusters. These things will remove all the dust on your dashboard and console in seconds.
Vomit Cleanup. Go ahead and pocket the cleaning fee and clean up the mess yourself.
Latex (or latex free) gloves. These are for the aforementioned vomit cleanup, but also any cleanup, maintenance, or whatever you need to do to your car. Last thing you want is greasy vomity hands.
Golf Umbrella. Whether this is for you or to help your customer, an oversize umbrella will really come in handy. Get one that is double canopy or windproof.
If you drive in the snow a lot, you need something to help if you lose traction. Traction mats can be very expensive, but these are the cheap ones and should do the trick.
And then that time you leave your lights on when you run in to grab a bite, and your battery is dead. This jumpstarter will allow you to jump your car with another person’s car to help. Of course, at a minimum, have jumper cables.
Emergency Roadside Kit. Hopefully you’ll never need it, but having flares, reflective signs, tow cables, medical kit, flashlight, etc will at least give you some peace of mind for all the hours you spend on the road.
What did I miss? What do you keep in your trunk?