I remember being at a game with my friend who'd put on an accumulator for correct score and first goalscorer. The first goalscorer bet came in. With the game in injury time, his score prediction was correct too. Because the home team were 2-0 up at this point, many fans were already leaving knowing the win was wrapped up, so we made our way to the exits, or at least to seats nearer the exit. While walking down the steps we looked up to see the opponents scoring a deflected consolation goal in which the ball seemed to trickle over the line in slow motion (it might even have crawled on to the post on its way in).
It was practically the last kick of the game, it made no difference to the outcome of the match (the home team still won) but it cost my friend about £250 from a £5 bet. He took it in surprisingly good humour.