wall of fuckwit
When you're shopping at a Tesco superstore (on your own, like a responsible person) and suddenly look down an aisle to see a stupid couple having an argument about what type of cheese to get right next to a member of staff stocking shelves, with two more random people discussing the weather further along.
Note to self: turn around and come back later -- no way you're getting through that wall of fuckwit just now.