I am sure some will disagree, but I think is is really annoying:

SHort stack opens to 15 from early position. I had been playing loose. I decided to raise him all in ($100 approximately). He quickly calls and I turn over JJ.

Board comes out all rags and then he shows AA.

WHat the hell is this shit? Turn over the AA once I show you JJ. WHy are you waiting? DO you plan to muck if a J hits? WHy? Who cares? Are you afraid we will know that you raise with AA and call an all in? That's come crucial information right there.

I think it's kind of a dick move not to show right away once I turn over the jacks. If I had a chance to pull a major slowroll on this guy I think it would have been appropriate to do so. He seemed like a nice guy and I know a lot of people do this, but I just don't get it.