The only event I have ever been to was a toys r us arceus event, which was memorable because I had to smuggle in my ds lite and download the god of Pokemon while my parents weren't paying attention. I was like a ninja.
It was probably the Pokemon World Championship 2009, it was my last tournament I've attended. That season overall was a great season. Many great accomplishments, friends, and memories.
The 10th Anniversary thing with all the downloads and what not. I still have the Celebi from that.. plus I got to beat up Misty with a level 70 Bulbasaur in Firered.