Borg Boy, hands down. I've written up the experience before. I'll dig it up and edit this reply to quote it.
Also, Jennifer Lien gave me a bad impression, though I've been told it was probably just shyness/nerves on her part. It just seemed very rude to me. The first time I saw her at a convention, as I was one or two from the head of the line at her autograph table, I heard her ask the staffer sitting beside her, "Do I have to talk to these people?"
ETA: Here's my account
of my encounter with Borg Boy.