Rented at BUF a couple times over the past year - standard Emerald Club, Midsize reservations:
Visit 1 - Assigned a 4 cyl Hyundai Sonata, elected to "downgrade" to a V6 Tiburon instead.
Visit 2 - Offered a choice of a Jeep Compass, Dodge Dakota Pickup, or a Dodge Journey as a complimentary "Emerald Club Upgrade." Guessing they were just out of cars at that point, and offering up whatever they had left.