Not driving. I get lost all the time, so I spent about 40% of time of roads I'm technically not supposed to be on and nothing great happens to me.
However, when I was in college, I had a ritual. Every morning, at the same time, I walked from my brownstone dorm, across Bay State Road and across Commonwealth Avenue. I crossed at the same light every day. I'd go to the Campus Conveneince and get a newspaper and the bagel shop for a wheat bagel.
One day, I woke up, something happened (can't remember what), but it put me in a really bad mood. I crossed Bay State Road and got to Commonwealth Avenue. I stood at the light and decided, just before it turned to give me a walk sign, that I was too angry to eat a bagel. So, I turned and walked down the same side of the street to go to a newspaper machine. I got my newspaper and, just as I started walking away from the machine, I heard a car squeeling. A car, driven by someone who we later found out fell asleep, hopped the curb and landed on the sidewalk. It landed right where the crosswalk is....right where I would have landed had I decided to cross the street in my usual ritual.
So, whatever put me in a bad mood that day, I'm SO HAPPY it happened.