A couple things happened to me actually
1) In high school, we were down 10-3 with about 3 minutes left in the match, we score a try under the posts and make the conversion to tie it up, then our opponent kicked to one of our players, who returned it all the way for the match winning try as time expired
2) The number amount of times I've come close to scoring a try for my university (as a prop) and failed to score. Possibly the most frustrating one was where my teammate, who was still learning to play the game, went down, and "released", but didn't let go of the ball, even when I tried to pick it up and practically walk it in, eventually the counterruck came and blew us off, needless to say, he got some glares from his teammates (like myself) after the match.
3) Our university team was having a Halloween match (for fun, where we play in our costumes), I picked up the ball and ran about 50m (the other team was about to let me score, since it was also my 21st birthday), as I was about to score, one of my opponents came and pushed me out of bounds. Needless to say, everyone got mad at him for that, but we all laughed in the end