I think 9/11 stands out in my life as the single most important event in the world to date. I remember the Challenger explosion, I was watching the launch live when it happened. I can still play the video back in my head. I think though that the Columbia explosion affected the world more.

Tiananmen Square stands out in my mind, it may not have changed the world, but it sure changed China. Recently there was a hostage taking at a school in Chechnya. Children were executed. That has forever redifined the definition of evil to me.

As a Canadian, I think our royal fsckup in Rwanda would be one event that changed my country forever. We were commanding the UN peacekeeping mission there and royally screwed up, there was a massive coverup, violent protests here, it changed us forever. Two other Canadian events would be the Montreal Ice Storm of 1998 and the Great Blackout of 2003, I imagaine quite a few Americans around here remember The Blackout.

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The town I went to college in was severely flooded in 2004, water was in our streets six feet deep. My basement had a foot of water in it. I was downtown when the storm hit. The sky was almost bright as day because of all the lightning around us, I could barely see across the street the rain was falling so thick, and the wind was so strong you got welts from the rain. It was as strong as a minor hurricane. I was in the streets when they sounded the civil defense siren, which had actually never been used. That's something you never forget. I was thinking "Is this a tornado, or a flood warning?" A tornado and I run into the basement. A flood, and I run for higher ground. Really had no idea what to do. I took cover in a store basement with a bunch of people until the water started rushing in and we figured it out. We got lucky, some people had to plucked off rooftops with police boats or helicopters. We were on slightly higher ground. That one didn't change the world though, it just changed me.
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Above all, though, the one event that sticks out in my mind, the first event I ever witnessed that changed the world, was the fall of the Berlin Wall in 1989. I was just old enough to understand its signifigance, why it was created, and had a basic grasp of what it meant to tear it down. My father woke me up out of bed at around 3am that day and sat me down to watch the first hammerfall. He asked me if I understood what the wall was, what it meant, and if I understood why people hated it so much. He explained to me that this was the first event I would bear witness to that would change the world forever. Until 9/11, it was my generation's JFK. I remember that more than Tiananmen Square because at the time, I did not understand what was happening in China, and I did not watch Tiananmen Square happen. Watching the first stones fall from the wall was the quintessential event in my life that taught me how easily one event can change the world, a lesson that served me well when the towers fell.

I can't believe nobody mentioned the moon landings yet...