As I've had some time to think about it, here's mine:
Actually it took me less than 2 seconds to think this is my best shot. Took this back 2004 in at the fish market in Santiago Chile. Took it with a point and shoot. Walking by, stopped, switched to B&W mode and took the picture and walked on. No flash, no processing, nothing, nothing has been done to this photo. Not that it couldn't use some processing.
The lack of processing isn't what makes this shot my best shot, it just reinforces the fact that there was a picture begging to be taken.
Side note, this was during the 2004 Summer Olympics. Chile had their first ever chance at a gold medal. Men's Doubles, I think. The city was going nuts.
Anyways, in the center of the fish market there's kind of food court. I got there for lunch and ended up getting caught in the moment, I ended up drinking pisco sours with a Peruvian Mariachi band and stayed until there until the wee hours of the morning. Walked my drunk ass back to the hotel.
Almost couldn't find the market the next day.