Corridor Alzheimer's
When someone is walking in a corridor, specifically and what seems to be most commonly right in front of you; they stop all of a sudden, look around with a clueless expression, sometimes with a sigh or a confusing mumble of inaudible words, and then start walking the opposite direction as if they forgot where they were even going in the first place.
It's already congested enough in these corridors, never mind when there are people with Corridor Alzheimer's that always seem to be in my way!