Yes, it depends on the rental agency but there are some out there. Dollar/Thrifty have some per day rental coupons/discounts.
Enterprise have some daily rate coupons you can apply.
Alamo/National/
Budget/
Avis/Hertz/Advantage have contract/corporate ID's that can apply discounts. In addition these agencies often have upgrade coupons you can apply.
Sometimes daily offers are limited, I have had best luck with Enterprise and Alamo.