I am a huge fan of Sixt. I have rented through them 3 times now, twice in Europe and once in the US. Their rental and pickup/drop-off processes are simple and straight forward. You never feel like you're being ripped off or discover hidden fees, the transparency is greatly appreciated. The vehicle range that is offered is also the best I have seen from a car rental company as well as the options you can add, such as snow tires and chains in Europe, all different types of child car seats, and more. I will continue to use Sixt as my preferred car rental company based on all of these factors.