The best cars to tow behind an RV are those that can be flat-towed. This means that they will not be damaged by being towed with all four wheels on the ground. Users should check the owner's manual to see each specific vehicle's requirements.
In general, it is important to make sure that the car will lubricate itself while being towed. Older, four-wheel-drive cars could often do this, as well as modern rear-wheel drive manual cars and four-wheel-drive cars with a manual transfer case that the owner can place in neutral. Some of the most popular choices are Jeep Wrangler, while a sportier option is the Nissan 370Z.