I was in Denver a little over a month ago and rented a car and it was super easy.
Call the Holiday Inn on Tower Rd by the airport and tell them to come get you. Once you get there go inside the lobby to the Enterprise Rent-A-Car and ask for Monica. She is a gorgeous young lady that went to OU. Tell her the tall, ripped, and handsome guy from KSU sent you there.
Maybe some small talk after talking about KSU's dominance over OU the past few years in football. Then ask for the cheapest option they have, she will look through the books and ask if you want a free upgrade. The free upgrade will be a Jeep Grand Cherokee for the same price as the cheap car.
Thank her for her time and drop a line like, "TBT will be back again soon". Drive off in your upgrade and enjoy the mountains courtesy of your bud TBT.