I agree with judolphin that using a discount code for a company you don't work for is wrong.
I'm afraid I disagree with you on that one!
I have never bought any vehicle made by Ford Motor Company since discovering the whacking great 40% discount they were giving a couple of the large UK banks a few years ago. To my "Retail Customer" mind, if Ford could afford to give corporates those sort of discounts, then it was the "Retail Punter" who was subsidising them!
Similarly, corporate Car Rental customers who enjoy big discounts are getting those discounts at my expense! A week's car hire should yield the same profit margin whether it's me renting a car or some company putting a sales rep in it. (In fact, I give a better profit margin because, by and large, I treat the car with a damn sight more respect than corporate employees!)
So, if I come across a corporate code that gives 60 bucks off, why shouldn't I take advantage?