People who can't walk in a straight line
Why? All you have to do is fix the target you're walking towards and just walk. It's not hard.
Near where I live is a place called Farnworth, and it's the home of what I like to call the Farnworth Walk. The exponent is usually about 40 and wearing tracky bottoms and a sheepskin jacket. It's not beyond the realms of possibility that he'll have slippers on too. He'll be eating a baked product containing offal and pubic hair purchased from Gregg's even though it's only half ten.
Armed with his steak and pube bake, he will walk down the padestrianised street at a snail's pace. Suddenly, with no warning, he will veer off to the left or right trampling anyone who gets in his way.
In Manchester, it's more subtle. They don't dress the same and they sort of follow an arc along the footpath, starting right at the curb, cutting in to the wall and back out to the curb over about 20 feet. If you're attempting an overtake on the right when they move out, they won't think twice about putting you in front of a bus.