Convention vendors. (Like you wouldn't believe! The worst ones were the underage kids that would just come up to the counter and talk about it. "When I'm 18, I'm gonna come in here and buy hentai." Graaa!!)
Hotdog vendors. (That's pretty sad. Atleast it isn't as bad as legal people into lolis (I think that's what they're called) though *shudders at the wrongness*)
Mmm.... lunch... (Seriously! And they'd just hang around for hours. Not buying anything. Just taking up space and being annoying. And no... not loli. >_< That's just... ew.)