Hmm... impressive things, eh?
The Fall of the Berlin Wall - It changed so much about the way we related to other countries.
The Rise of 24 Hour New Channels - And all the side effects thereof.
The Mars Pathfinder Rover
Gulf War I - The first televised military operation that showed the potential of laser guided munitions and stealth technology.
The Rise of the World Wide Web - I still remember my initial thoughts after trying it out ("WTF? This is taking forever to load. This will never catch on.")
The Global Positioning System is developed and later opened up to civilian use
The humanitarian response to the 2004 Boxing Day Tsunami - Probably the largest humanitarian effort the world has ever seen.
That probably covers it.