I just recalled that for about 3 years I was focused on analysing sports results, particularly English Premier League soccer. I got hold of 10 years worth of data and built some large spreadsheets with it. I spotted that there had been an unusually long period where the number of 3-0 results had been below the long term average, and convinced myself that this had to correct itself fairly soon. So I started betting on every team to win 3-0. And sure enough, the average picked up again and I beat the odds. I was only betting as a hobby and with money I could afford to lose. But as it turned out I was £600 up at the end of the season.