Anything from "children run onto the street to chase after a ball they were playing with" to "pedestrian jumping out between cars because they didn't see you" or "tram stops in the middle of the road and people exit onto the street".
Legally pedestrians must use marked crossings when available and are told to check both ways, but if a driver hits a pedestrian, it's always the driver's fault (though the pedestrian might share some blame in some circumstances but never the full liability).