People who sit on their phones the entire time in shul during tefilla. Seriously, why bother even coming?
Since when did it become "OK" to just sit back and be immersed in your phone from the time you throw on your talis/tefillin until the moment you decide you had enough and just as coldly throw off your talis/tefillin and go home, or worse, not even realize that the tefilla is over and you have to hide your very red face as you egress even faster.
The same goes for mincha and maariv, it seems that the new norm is to come in, sit down, and pull out the phone and depending on what the guy is doing with the phone he might not even go through the motions at all and simply stay seated the whole time.
Don't even get me started on the ones who have the utter chutzpah to answer during davening. Shame on them! There's no excuse in the world for that, not even a Dr has a right to answer in middle of tefilla in middle of the shul, at least let him walk out.
End rant.