The most important event I've ever seen (fully and comprehensibly) was the election of President Obama on TV as the first black president (and because I kind of thought he'd be assassinated during the inauguration speech). And the most important thing(S) I've seen were small babies. It's like an object and a thing but you know it's just like you, and will be old and will laugh and will cry, and eventually die. But it's amazing to watch such a fresh start.
Hard to pick just one. But today in my mind, the most important thing I saw was a presentation given on human trafficking and how rampant it is. Slavery is still going strong and too many people are ignorant of this fact. It opened my eyes to the world around me and I just can't ignore these heinous crimes any longer.
The most important thing I ever saw was my son when they laid him down beside me right after he was born. Anything else pales after that.
Many facets to this question, I think. If we are talking world events, there are a few that I 'witnessed' during my childhood that made big impressions on me, and led to some to some early thought processes about the world around me - namely the fall of Ceausescu, the fall of the Berlin wall & the fall of the Soviet Union. I was around 9/10. Speaking more about my own life, I think these last two years I learned some important life lessons about people and their motivations at times, and I guess sometimes hard lessons are the best kind. More positively, nothing is more important to me than to see/feel any love or support I have in my life, especially from family. I just hope they feel it coming back to them from me.
On a personal level it is a no brainer: the birth of my son. As for world events there are plenty I witnessed on TV. But as far as important world events that I witnessed in person? I think that would have to be the revolution in Libya breaking out. I was stationed at the US embassy in Tripoli when it occured and the things I witnessed with my own eyes, some amazing and some horendous, will forever be frozen in my mind.