Down here in the DC area we have a lousy bagel chain called Manhattan Bagels. The name is a cruel joke; the bagels are mushballs.
Nevertheless, I was feeling charitable towards my fellow slaves and I remembered that there was a Manhattan Bagel coupon in the Entertainment book. Sure enough, a coupon for up to two dozen bagels at 50% off. The back of the coupon listed four locations that didn't include the one I was going to go to, but I figured that would be no problem, since I knew they had a sign in the window that said "We accept all competitors' coupons."
So I walked in and showed the doofus behind the counter my coupon. He immediately and pretty violently shook his no. No, as in we don't accept that coupon.
Rest assured that I will be using some competitors' coupons (i.e, coupons from other third-rate bagel joints that I have no intention of patronizing anyway) at this dump in the very near future.