Aerosol Taco Sauce.
I've encountered quite a few black bear in my time. Most were a good distance away (100 yards or more), and either didn't know that I was there, or chose to ignore me. A couple of times, I've come upon them at a much closer distance, much to our mutual surprise, and my fright. It's (in hindsight) funny to see them give a little jolt, turn and walk away as fast as possible. More times than not, they've smelled me before I see them. I know a guy who literally bumped into a big black bear while picking blueberries in northern Ontario. The bear was doing the same thing, and they backed into each other, turned, looked and slowly backed off, both scared to death.
They are damned fast swimmers, too. While canoeing, I once snuck up on what I thought was a swimming beaver, only to discover, at about 6' away, that it was half of a bear's head poking out of the water! I backed off and watched her swim for a mile or so...just beautiful.
Then, two years ago, I went outside at my house to see what the dogs were barking at, only to discover a young black bear watching them go crazy. He quickly walked away and quickly vanished into the woods.
Bears are wonderful to see, but they don't consider us as warm and fuzzy as we do them. I think that they they see us as a threat that could possibly be a meal.