The 50 move rule?

 I've had a couple of interesting experiences with the 50 move rule over the years. During the last round of a past Sydney International Open, 2 players dragged the game well beyond the point where they could claim, one because he thought he was winning (at that stage he was not), and the other because he thought you could only claim if there were no pawns on the board (NB This was prior to the 75 move rule coming into effect).

Going in the other direction, it appears a recent game at a tournament I was the arbiter for ended in a draw after the players reached move 50 and basically agreed that the game was drawn. Note: this was 50 moves in total, starting from move 1, with plenty of pawn moves and captures being played during the game. Both were new juniors, so I can't really blame them, although they simply recorded the result, without checking with me first!

It did remind of a case from an Olympiad(!) where an arbiter stepped in to declare the game drawn after 75 moves, misunderstanding the then new 75 move rule, thinking it applied from move 1, rather than from the last pawn move/capture. The game was quickly resumed, although I'm not sure what happened to the arbiter