The ones I really hate are zebra crossings right on top of roundabouts. Near my parents there is a triple roundabout with zebras on every exit and suicidal pedestrians who dont look before they run into the road.
They recently did this at my uni. Busy main road with a roundabout to turn down a side road which is the access to uni. They went and put zebras across literally on the corner of the roundabout. This of course has meant that theres been a shedload more near misses than before when people come round the roundabout to go to uni and then have to slam on the brakes because of the crossing, putting them directly in the way of the main flow of traffic.
What makes it worse is that these kinds of crossings usually have loads of alternatives. Within 100m there is not only a traffic light pedestrian crossing, but an underpass, and another zebra crossing but well away from the roundabout.
Theres another example I hate where theres a big school, and they put traffic light crossings across. There is also an overpass next to it. The obvious happens, no one uses the overpass, preferring to have the lights going nearly constantly, resulting in BIG traffic queues. What they need to do is get lollipop ladies out with a key or something which is the only way to activate the lights at school times. This way they can regulate how often they go. At the moment I find it such a waste of time/resources to have a lollipop lady/man stood at a crossing and essentially just pressing the button for the kids as they come up.