If you are out in good moose country in the prime heat of the rut, it is hard to keep a bull away from you. I have been chased up a tree by one and a friend, who was a game warden, was twice chased up a tree in the same fall!
Just walking through the bush once attracted a bull to me. I didn't want to shoot him, so to try and get rid of him, I shot a hole through his antler with my 30-06. He never even batted an eye!
Another time a really ###y bull, actually horrible looking, with heavy drooling and panting, approached me on an alder slide of a mountain. I seriously thought I was going to have to shoot him, as I couldn't get away. If I stood perfectly still, he couldn't make me out. But, as soon as I moved, to try and get further away, he would charge closer. From thirty feet it was just plain scary!
Finally got away and ¼ mile down the slide and closer to my vehicle. I gave a cow call, and he came charging down the mountain. A quick sprint to the vehicle and I'm gone!