People who walk slowly on the pavement or (even worse) couples or groups who insist on walking abreast of each other.

Devious, underhand individuals who disappear when it's their turn to buy me a drink.

Going to the supermarket and getting a trolley that (once there is some weight in it) constantly veers in one direction, requiring no small exertion to get it to go in the opposite one.

Going to the toilet in a pub only to discover (post main event) that there is no toilet paper/soap/hot water.