Tell them you feel uncomfortable with them around, directly. Don't just sugar coat it. Just be like "Yo, no offense, but really, it's a bit uncomfortable with you around. We kind of just want to enjoy this con together, and you're really kind of ruining the experience here." To my knowledge / understanding, most creepy guys are really just awkward lol. So the direct confrontation should scare them away and "wake them up" as to how uncomfortable they're really making you feel, and that'll be enough to get them to go away. If he keeps being persistent though.. call da po-poz on dat fool. And tell them he's being a fcking weirdo / stalker. I hear con authorities don't take no sht from these scenarios lol, so you won't have to worry about him after that. gl!