This retailer obv had massive campaigns for black friday, but also obv very shitty and inflexible systems.
This buddy of mine found that the black friday promotions pricings import failed 5 min before midnight. Meaning that not only would there be no black friday pricing, there would be no pricing at all on the site for 24h until the next pricing run.
He pulled some heroics and managed to fix the import in time and black friday was a success.
So he saved the company 5M GBP in profits, singlehandedly.
As a thanks he got a 25 GBP gift card to the same site.