Forgotten Coupon
In college I bought a pack of coupons for Hungry Howie’s Pizza. It had three coupons for a free pizza, no other requirements, just a completely free pizza. I would call and order my pizza, tell them that I had the coupon for a free pizza, show up and “forget” to give them the coupon every time.
I always had it on me as a backup, just in case they did ask for it. But, out of the three coupons, they only asked for it once. I kept using them for months, until the coupons expired, which I am sure they were looking for.
I ended up getting a few dozen free pizzas out of them, which was great for a college student.
Story credit: Reddit / Spe1025