Trade show and 'Bingo' card follow up. You are wasting lot's of money, and lost opportunity, if you simply send out the literature. With the cards, it's been ages since they circled your number, along with many others. Plus, your sales people tend not to follow up as promptly as they should. Call them, promptly, to find out what they really want, and why.
Service calls to a business or home.
If so, no doubt you realize they are your best, or worst, sales person. They hand out 'reply cards' asking the customer to send it back to you. If you learn something was broken, fix it, and you will likely recover from the damage. Health care provider gets a new patient. They came to your office for the first time.