Rental Giant is a term used to describe two of the largest rental companies in the world, Avis and Uhaul. Avis is a car rental company that was founded in 1946 and has over 5, 000 locations in 165 countries. Uhaul is a moving and storage company that was founded in 1945 and has over 20, 000 locations in the United States and Canada. Both companies are known for their competitive prices and excellent customer service.