A few years ago. Crystal Palace were 3 games away from the end of the season and far, far adrift from the rest of the pack. Certain to go down. The manager was sacked and the assistant had taken over and they won their last two games and had a chance of survival, albeit a slim one.
Anyway, one of the results had gone ok but the other team, who Palace needed to get a better score than were ahead. Suddenly in the 80th minute they conceded leaving Palace ready for the win. In the 90th minute Palace scored

Securing their palace in the league.
Also when Arsenal one the Premership at old Trafford. When Arsenal came back from 2 - 0 at half time to 3 -2 at full time with Henry scoring the final goal in the last moments of the game. I quite liked the Liverpool vs Arsenal game (4-4) from this season though.