I'm wicked shy IRL, so mine's not going to be very interesting.
Last con, October, I wore my mostly finished Drossel cosplay. Not many people seemed to notice or care, probably because it was pretty crappy and I hadn't put the buttons on and my hat broke ten minutes into the convention. It was a mess. But as I was waiting to be picked up (we didn't drive since the convention was ten minutes from 'home' and we were too cheap to pay for parking) this guy walks past humming London Bridge.
So yeah, not the most interesting thing, but it beat being passed up for Grell like I was all day.