There's nothing that elicits a better reaction from a coach more than a bad call by an official.
Sure, coaches get pretty upset when their players make mistakes, but the anger, exasperation, and shock increases that much more when they don't agree with a referee's call.
Monday night during the Bruins and Senators game, a call that Guy Boucher didn't agree with was made, and his reaction was pure shock to say the least.
As you can imagine, the internet had a field day with some of the faces Boucher made.
The reaction was all for not at the end of the day, though, as the call didn't go against Ottawa. Still, an incredible meme face came out of it, so there's that, and Ottawa won 4-2. (H/T: /r/hockey)