Well, for me its the fact that I get to dress up, and sometimes people ask to take my picture and it's really cool when that happens ^__^
Also, at every con I go to, there is this awesome guy called the Savage Bandito, and something wacky always happens with him.
For example, at Anime North, I ate 3/4 of a tin of Nintendo Power mints...all at once. ....When I left, there was a puddle of goo on the floor XD
Another awesome thing is sometimes people fight with their fake weapons, or hold cool photoshoots that rock. XD