Boarding Cards
I think it's funny when pax board and you ask to see their boarding card and they don't show it to you they just say "I'm with her" and indicate the person in front!!
Also, our fwd crew member has to stand at the bottom of the steps for boarding, and pax come to the front with row 20 seats for example. When I say that they need to board at the back, they argue and say "well we've been told to get on at the front".
One particular person stood there arguing with me and I said something along the lines of "We board rows 1-15 at the front and 16-30 at the rear, therefore not causing congestion inside the cabin and making it easier and less time consuming to board", well they weren't happy with that, because they'd been already told to get on at the front and thought I was just trying to make their day difficult. They spent the whole flight glaring at me and making me feel uncomfortable. I'd not even been rude or abrupt, I'd just explained why. It's not my fault that the handling agent had given out the wrong info...