People without a doubt.
I can fly at my field any day, I can shop online with the vendors any day...
But getting to see old friends like this only comes once a year. I may see some at other events, but to have everyone together at SEFF just makes it magic on a scale like no other.
It truly is the "Fellowship Electric"
http://www.youtube.com/watch?v=Q6ckQs2XpS8