This one may be odd, or I may not be alone:
When, going through a set of double doors, someone entering as you are leaving won't bother to open the door on their side, but instead waits to dive through the door on your side after you. Quite possibly getting in your way by being too close to where you would be exiting.
I don't understand why so many people do this unless they have their hands full or something. Really, it's not that big of a task to pull a door open and it would be quicker than waiting for me to get out of the door.