I beat all of the original five campaigns for Left 4 Dead 2 on Expert a few months back. I also beat Dead Center on Expert Realism with help from a few good friends.

As for competitive games, I was playing a match of King of the Hill on Academy in Gears of War 3. The score was 142-140 when the other team spawned at the final hill of the game and captured it. As doing nothing meant my team lost, I threw my smoke grenade and managed to stun the entire other team. I was able to roadie run between the four Locust there, break the hill at 149 points, and kill one of them with my shotgun before I went down. However, I bought enough time for my team to arrive at the hill and clean up the enemy team to win the match.