During nesting season, the entire back half of my backyard is effectively inaccessible because the Canada geese will attack you if you come within hundreds of feet of their nest. They are also utterly fearless and would also attack cars that come too far down the driveway (while still being nowhere near the nest.)

Their behavior definitely varies situationally, I have been to parks where there were hundreds of them and the only problem from them was the enormous amount of feces.