I heard some people say that the sai, a fork like weapon which is perhaps best known through the character of Raphael from Ninja Turtles, has been known to snap sword blades. I don't know if this would be possible, a sai can be used to catch a sword blade but as for snapping it, from what I know sword blades were really strong as well as flexible and to catch a sword blade in a sai it would most likely become a tug of war but it would not result in a broken sword blade. I do know that in the middle ages in Europe they did have this weapon called the sword breaker which was also used to catch and in some cases break sword blades, but in the case of the blade breaking, that would be if it was one of those skinny fencing swords, not the broadswords used by the knights or for that matter a sword like the katana.