Watching the 2016 AL Wild Card game between Toronto and Baltimore (that Edwin Encarnacion won with a walk-off), and I'm seeing what might be considered a balk, but I'm not sure why it's not.
Roberto Osuna pitched in relief in this game. His delivery was smooth and normal, like most pitchers. However, he altered his delivery in only certain situations (2-strike count, looking to put the batter away). I'm not sure he even did it more than once or twice.
Here is a clip of that game and the delivery in question.
Now, with Daisuke Matsuzaka, I can understand the argument that it wouldn't be called as a balk because his hitch is part of his delivery. But wouldn't hitching in your delivery as an exception be considered as intentionally trying to deceive the batter?