My first con experience was at "Hal-Con" here in eastern Canada this past fall. It's a broad based con featuring SF, fantasy, comics, etc. Although the featured guests were Denise Crosby and Walter Koenig, there were a number of authors, comic book artist, video game developers, etc in attendance.
I went because of the costuming, and I spent a long time building a tribute to Master Chief from the Halo games. It was very well received, and at one point I was posing at the top of a small flight of stairs for pictures. There was a huge roar of laughter from the crowd and I turned to see Denise Crosby had crept up behind me and given me "bunny ears".